Refs #26022 -- Used context manager version of assertRaisesMessage in tests.

21 files changed, 584 insertions, 566 deletions

diff --git a/tests/admin_registration/tests.py b/tests/admin_registration/tests.py
index ffca76886e..c1efae76c7 100644
--- a/tests/admin_registration/tests.py
+++ b/tests/admin_registration/tests.py
@@ -127,12 +127,12 @@ class TestRegistrationDecorator(SimpleTestCase):
         self.default_site.unregister(Place)
 
     def test_wrapped_class_not_a_model_admin(self):
-        self.assertRaisesMessage(ValueError, 'Wrapped class must subclass ModelAdmin.',
-            register(Person), CustomSite)
+        with self.assertRaisesMessage(ValueError, 'Wrapped class must subclass ModelAdmin.'):
+            register(Person)(CustomSite)
 
     def test_custom_site_not_an_admin_site(self):
-        self.assertRaisesMessage(ValueError, 'site must subclass AdminSite',
-            register(Person, site=Traveler), NameAdmin)
+        with self.assertRaisesMessage(ValueError, 'site must subclass AdminSite'):
+            register(Person, site=Traveler)(NameAdmin)
 
     def test_empty_models_list_registration_fails(self):
         with self.assertRaisesMessage(ValueError, 'At least one model must be passed to register.'):
diff --git a/tests/auth_tests/test_models.py b/tests/auth_tests/test_models.py
index 6256f484da..e5b00f5f29 100644
--- a/tests/auth_tests/test_models.py
+++ b/tests/auth_tests/test_models.py
@@ -161,11 +161,8 @@ class UserManagerTestCase(TestCase):
         self.assertEqual(returned, 'email\ with_whitespace@d.com')
 
     def test_empty_username(self):
-        self.assertRaisesMessage(
-            ValueError,
-            'The given username must be set',
-            User.objects.create_user, username=''
-        )
+        with self.assertRaisesMessage(ValueError, 'The given username must be set'):
+            User.objects.create_user(username='')
 
     def test_create_user_is_staff(self):
         email = 'normal@normal.com'
diff --git a/tests/custom_columns/tests.py b/tests/custom_columns/tests.py
index 2b5526453f..7102e4fdbe 100644
--- a/tests/custom_columns/tests.py
+++ b/tests/custom_columns/tests.py
@@ -91,31 +91,22 @@ class CustomColumnsTests(TestCase):
         self.assertEqual(self.a1, Author.objects.get(first_name__exact='John'))
 
     def test_filter_on_nonexistent_field(self):
-        self.assertRaisesMessage(
-            FieldError,
+        msg = (
             "Cannot resolve keyword 'firstname' into field. Choices are: "
-            "Author_ID, article, first_name, last_name, primary_set",
-            Author.objects.filter,
-            firstname__exact='John'
+            "Author_ID, article, first_name, last_name, primary_set"
         )
+        with self.assertRaisesMessage(FieldError, msg):
+            Author.objects.filter(firstname__exact='John')
 
     def test_author_get_attributes(self):
         a = Author.objects.get(last_name__exact='Smith')
         self.assertEqual('John', a.first_name)
         self.assertEqual('Smith', a.last_name)
-        self.assertRaisesMessage(
-            AttributeError,
-            "'Author' object has no attribute 'firstname'",
-            getattr,
-            a, 'firstname'
-        )
+        with self.assertRaisesMessage(AttributeError, "'Author' object has no attribute 'firstname'"):
+            getattr(a, 'firstname')
 
-        self.assertRaisesMessage(
-            AttributeError,
-            "'Author' object has no attribute 'last'",
-            getattr,
-            a, 'last'
-        )
+        with self.assertRaisesMessage(AttributeError, "'Author' object has no attribute 'last'"):
+            getattr(a, 'last')
 
     def test_m2m_table(self):
         self.assertQuerysetEqual(
diff --git a/tests/distinct_on_fields/tests.py b/tests/distinct_on_fields/tests.py
index 9e53ce3ae9..f999f76c4a 100644
--- a/tests/distinct_on_fields/tests.py
+++ b/tests/distinct_on_fields/tests.py
@@ -90,11 +90,8 @@ class DistinctOnTests(TestCase):
 
         # Combining queries with different distinct_fields is not allowed.
         base_qs = Celebrity.objects.all()
-        self.assertRaisesMessage(
-            AssertionError,
-            "Cannot combine queries with different distinct fields.",
-            lambda: (base_qs.distinct('id') & base_qs.distinct('name'))
-        )
+        with self.assertRaisesMessage(AssertionError, "Cannot combine queries with different distinct fields."):
+            base_qs.distinct('id') & base_qs.distinct('name')
 
         # Test join unreffing
         c1 = Celebrity.objects.distinct('greatest_fan__id', 'greatest_fan__fan_of')
diff --git a/tests/expressions/tests.py b/tests/expressions/tests.py
index c7b7a7a15c..1040bd4b63 100644
--- a/tests/expressions/tests.py
+++ b/tests/expressions/tests.py
@@ -318,7 +318,8 @@ class BasicExpressionsTests(TestCase):
             'expressions.Company.num_employees. F() expressions can only be '
             'used to update, not to insert.'
         )
-        self.assertRaisesMessage(ValueError, msg, acme.save)
+        with self.assertRaisesMessage(ValueError, msg):
+            acme.save()
 
         acme.num_employees = 12
         acme.name = Lower(F('name'))
@@ -327,7 +328,8 @@ class BasicExpressionsTests(TestCase):
             'expressions.Company.name))" on expressions.Company.name. F() '
             'expressions can only be used to update, not to insert.'
         )
-        self.assertRaisesMessage(ValueError, msg, acme.save)
+        with self.assertRaisesMessage(ValueError, msg):
+            acme.save()
 
     def test_ticket_11722_iexact_lookup(self):
         Employee.objects.create(firstname="John", lastname="Doe")
diff --git a/tests/file_storage/tests.py b/tests/file_storage/tests.py
index 28a09ae557..b5ff073525 100644
--- a/tests/file_storage/tests.py
+++ b/tests/file_storage/tests.py
@@ -574,10 +574,8 @@ class FileFieldStorageTests(TestCase):
             # Testing exception is raised when filename is too short to truncate.
             filename = 'short.longext'
             objs[0].limited_length.save(filename, ContentFile('Same Content'))
-            self.assertRaisesMessage(
-                SuspiciousFileOperation, 'Storage can not find an available filename',
-                objs[1].limited_length.save, *(filename, ContentFile('Same Content'))
-            )
+            with self.assertRaisesMessage(SuspiciousFileOperation, 'Storage can not find an available filename'):
+                objs[1].limited_length.save(*(filename, ContentFile('Same Content')))
         finally:
             for o in objs:
                 o.delete()
diff --git a/tests/fixtures_regress/tests.py b/tests/fixtures_regress/tests.py
index 5edd1c722f..6b4a3f7673 100644
--- a/tests/fixtures_regress/tests.py
+++ b/tests/fixtures_regress/tests.py
@@ -537,14 +537,8 @@ class TestFixtures(TestCase):
         settings.FIXTURE_DIRS cannot contain duplicates in order to avoid
         repeated fixture loading.
         """
-        self.assertRaisesMessage(
-            ImproperlyConfigured,
-            "settings.FIXTURE_DIRS contains duplicates.",
-            management.call_command,
-            'loaddata',
-            'absolute.json',
-            verbosity=0,
-        )
+        with self.assertRaisesMessage(ImproperlyConfigured, "settings.FIXTURE_DIRS contains duplicates."):
+            management.call_command('loaddata', 'absolute.json', verbosity=0)
 
     @skipIfNonASCIIPath
     @override_settings(FIXTURE_DIRS=[os.path.join(_cur_dir, 'fixtures')])
@@ -553,16 +547,13 @@ class TestFixtures(TestCase):
         settings.FIXTURE_DIRS cannot contain a default fixtures directory
         for application (app/fixtures) in order to avoid repeated fixture loading.
         """
-        self.assertRaisesMessage(
-            ImproperlyConfigured,
+        msg = (
             "'%s' is a default fixture directory for the '%s' app "
             "and cannot be listed in settings.FIXTURE_DIRS."
-            % (os.path.join(_cur_dir, 'fixtures'), 'fixtures_regress'),
-            management.call_command,
-            'loaddata',
-            'absolute.json',
-            verbosity=0,
+            % (os.path.join(_cur_dir, 'fixtures'), 'fixtures_regress')
         )
+        with self.assertRaisesMessage(ImproperlyConfigured, msg):
+            management.call_command('loaddata', 'absolute.json', verbosity=0)
 
     @override_settings(FIXTURE_DIRS=[os.path.join(_cur_dir, 'fixtures_1'),
                                      os.path.join(_cur_dir, 'fixtures_2')])
@@ -734,41 +725,37 @@ class NaturalKeyFixtureTests(TestCase):
         )
 
     def test_dependency_sorting_tight_circular(self):
-        self.assertRaisesMessage(
+        with self.assertRaisesMessage(
             RuntimeError,
             "Can't resolve dependencies for fixtures_regress.Circle1, "
-            "fixtures_regress.Circle2 in serialized app list.",
-            serializers.sort_dependencies,
-            [('fixtures_regress', [Person, Circle2, Circle1, Store, Book])],
-        )
+            "fixtures_regress.Circle2 in serialized app list."
+        ):
+            serializers.sort_dependencies([('fixtures_regress', [Person, Circle2, Circle1, Store, Book])])
 
     def test_dependency_sorting_tight_circular_2(self):
-        self.assertRaisesMessage(
+        with self.assertRaisesMessage(
             RuntimeError,
             "Can't resolve dependencies for fixtures_regress.Circle1, "
-            "fixtures_regress.Circle2 in serialized app list.",
-            serializers.sort_dependencies,
-            [('fixtures_regress', [Circle1, Book, Circle2])],
-        )
+            "fixtures_regress.Circle2 in serialized app list."
+        ):
+            serializers.sort_dependencies([('fixtures_regress', [Circle1, Book, Circle2])])
 
     def test_dependency_self_referential(self):
-        self.assertRaisesMessage(
+        with self.assertRaisesMessage(
             RuntimeError,
             "Can't resolve dependencies for fixtures_regress.Circle3 in "
-            "serialized app list.",
-            serializers.sort_dependencies,
-            [('fixtures_regress', [Book, Circle3])],
-        )
+            "serialized app list."
+        ):
+            serializers.sort_dependencies([('fixtures_regress', [Book, Circle3])])
 
     def test_dependency_sorting_long(self):
-        self.assertRaisesMessage(
+        with self.assertRaisesMessage(
             RuntimeError,
             "Can't resolve dependencies for fixtures_regress.Circle1, "
             "fixtures_regress.Circle2, fixtures_regress.Circle3 in serialized "
-            "app list.",
-            serializers.sort_dependencies,
-            [('fixtures_regress', [Person, Circle2, Circle1, Circle3, Store, Book])],
-        )
+            "app list."
+        ):
+            serializers.sort_dependencies([('fixtures_regress', [Person, Circle2, Circle1, Circle3, Store, Book])])
 
     def test_dependency_sorting_normal(self):
         sorted_deps = serializers.sort_dependencies(
@@ -830,13 +817,12 @@ class M2MNaturalKeyFixtureTests(TestCase):
         Resolving circular M2M relations without explicit through models should
         fail loudly
         """
-        self.assertRaisesMessage(
+        with self.assertRaisesMessage(
             RuntimeError,
             "Can't resolve dependencies for fixtures_regress.M2MSimpleCircularA, "
-            "fixtures_regress.M2MSimpleCircularB in serialized app list.",
-            serializers.sort_dependencies,
-            [('fixtures_regress', [M2MSimpleCircularA, M2MSimpleCircularB])]
-        )
+            "fixtures_regress.M2MSimpleCircularB in serialized app list."
+        ):
+            serializers.sort_dependencies([('fixtures_regress', [M2MSimpleCircularA, M2MSimpleCircularB])])
 
     def test_dependency_sorting_m2m_complex(self):
         """
diff --git a/tests/forms_tests/tests/test_fields.py b/tests/forms_tests/tests/test_fields.py
index b46f897391..c4798076d3 100644
--- a/tests/forms_tests/tests/test_fields.py
+++ b/tests/forms_tests/tests/test_fields.py
@@ -96,8 +96,10 @@ class FieldsTests(SimpleTestCase):
         f = CharField()
         self.assertEqual('1', f.clean(1))
         self.assertEqual('hello', f.clean('hello'))
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
         self.assertEqual('[1, 2, 3]', f.clean([1, 2, 3]))
         self.assertEqual(f.max_length, None)
         self.assertEqual(f.min_length, None)
@@ -135,7 +137,8 @@ class FieldsTests(SimpleTestCase):
 
     def test_charfield_5(self):
         f = CharField(min_length=10, required=True)
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
         msg = "'Ensure this value has at least 10 characters (it has 5).'"
         with self.assertRaisesMessage(ValidationError, msg):
             f.clean('12345')
@@ -193,18 +196,23 @@ class FieldsTests(SimpleTestCase):
     def test_integerfield_1(self):
         f = IntegerField()
         self.assertWidgetRendersTo(f, '<input type="number" name="f" id="id_f" />')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual(1, f.clean('1'))
         self.assertIsInstance(f.clean('1'), int)
         self.assertEqual(23, f.clean('23'))
-        self.assertRaisesMessage(ValidationError, "'Enter a whole number.'", f.clean, 'a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a whole number.'"):
+            f.clean('a')
         self.assertEqual(42, f.clean(42))
-        self.assertRaisesMessage(ValidationError, "'Enter a whole number.'", f.clean, 3.14)
+        with self.assertRaisesMessage(ValidationError, "'Enter a whole number.'"):
+            f.clean(3.14)
         self.assertEqual(1, f.clean('1 '))
         self.assertEqual(1, f.clean(' 1'))
         self.assertEqual(1, f.clean(' 1 '))
-        self.assertRaisesMessage(ValidationError, "'Enter a whole number.'", f.clean, '1a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a whole number.'"):
+            f.clean('1a')
         self.assertEqual(f.max_value, None)
         self.assertEqual(f.min_value, None)
 
@@ -217,31 +225,38 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(1, f.clean('1'))
         self.assertIsInstance(f.clean('1'), int)
         self.assertEqual(23, f.clean('23'))
-        self.assertRaisesMessage(ValidationError, "'Enter a whole number.'", f.clean, 'a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a whole number.'"):
+            f.clean('a')
         self.assertEqual(1, f.clean('1 '))
         self.assertEqual(1, f.clean(' 1'))
         self.assertEqual(1, f.clean(' 1 '))
-        self.assertRaisesMessage(ValidationError, "'Enter a whole number.'", f.clean, '1a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a whole number.'"):
+            f.clean('1a')
         self.assertEqual(f.max_value, None)
         self.assertEqual(f.min_value, None)
 
     def test_integerfield_3(self):
         f = IntegerField(max_value=10)
         self.assertWidgetRendersTo(f, '<input max="10" type="number" name="f" id="id_f" />')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual(1, f.clean(1))
         self.assertEqual(10, f.clean(10))
-        self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 10.'", f.clean, 11)
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 10.'"):
+            f.clean(11)
         self.assertEqual(10, f.clean('10'))
-        self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 10.'", f.clean, '11')
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 10.'"):
+            f.clean('11')
         self.assertEqual(f.max_value, 10)
         self.assertEqual(f.min_value, None)
 
     def test_integerfield_4(self):
         f = IntegerField(min_value=10)
         self.assertWidgetRendersTo(f, '<input id="id_f" type="number" name="f" min="10" />')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
-        self.assertRaisesMessage(ValidationError, "'Ensure this value is greater than or equal to 10.'", f.clean, 1)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is greater than or equal to 10.'"):
+            f.clean(1)
         self.assertEqual(10, f.clean(10))
         self.assertEqual(11, f.clean(11))
         self.assertEqual(10, f.clean('10'))
@@ -252,14 +267,17 @@ class FieldsTests(SimpleTestCase):
     def test_integerfield_5(self):
         f = IntegerField(min_value=10, max_value=20)
         self.assertWidgetRendersTo(f, '<input id="id_f" max="20" type="number" name="f" min="10" />')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
-        self.assertRaisesMessage(ValidationError, "'Ensure this value is greater than or equal to 10.'", f.clean, 1)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is greater than or equal to 10.'"):
+            f.clean(1)
         self.assertEqual(10, f.clean(10))
         self.assertEqual(11, f.clean(11))
         self.assertEqual(10, f.clean('10'))
         self.assertEqual(11, f.clean('11'))
         self.assertEqual(20, f.clean(20))
-        self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 20.'", f.clean, 21)
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 20.'"):
+            f.clean(21)
         self.assertEqual(f.max_value, 20)
         self.assertEqual(f.min_value, 10)
 
@@ -278,8 +296,10 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(1, f.clean(' 1.0 '))
         self.assertEqual(1, f.clean('1.'))
         self.assertEqual(1, f.clean(' 1. '))
-        self.assertRaisesMessage(ValidationError, "'Enter a whole number.'", f.clean, '1.5')
-        self.assertRaisesMessage(ValidationError, "'Enter a whole number.'", f.clean, '…')
+        with self.assertRaisesMessage(ValidationError, "'Enter a whole number.'"):
+            f.clean('1.5')
+        with self.assertRaisesMessage(ValidationError, "'Enter a whole number.'"):
+            f.clean('…')
 
     def test_integerfield_big_num(self):
         f = IntegerField()
@@ -304,24 +324,31 @@ class FieldsTests(SimpleTestCase):
     def test_floatfield_1(self):
         f = FloatField()
         self.assertWidgetRendersTo(f, '<input step="any" type="number" name="f" id="id_f" />')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual(1.0, f.clean('1'))
         self.assertIsInstance(f.clean('1'), float)
         self.assertEqual(23.0, f.clean('23'))
         self.assertEqual(3.1400000000000001, f.clean('3.14'))
         self.assertEqual(3.1400000000000001, f.clean(3.14))
         self.assertEqual(42.0, f.clean(42))
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, 'a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('a')
         self.assertEqual(1.0, f.clean('1.0 '))
         self.assertEqual(1.0, f.clean(' 1.0'))
         self.assertEqual(1.0, f.clean(' 1.0 '))
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, '1.0a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('1.0a')
         self.assertEqual(f.max_value, None)
         self.assertEqual(f.min_value, None)
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, 'Infinity')
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, 'NaN')
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, '-Inf')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('Infinity')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('NaN')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('-Inf')
 
     def test_floatfield_2(self):
         f = FloatField(required=False)
@@ -334,11 +361,10 @@ class FieldsTests(SimpleTestCase):
     def test_floatfield_3(self):
         f = FloatField(max_value=1.5, min_value=0.5)
         self.assertWidgetRendersTo(f, '<input step="any" name="f" min="0.5" max="1.5" type="number" id="id_f" />')
-        self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 1.5.'", f.clean, '1.6')
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value is greater than or equal to 0.5.'",
-            f.clean, '0.4'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 1.5.'"):
+            f.clean('1.6')
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is greater than or equal to 0.5.'"):
+            f.clean('0.4')
         self.assertEqual(1.5, f.clean('1.5'))
         self.assertEqual(0.5, f.clean('0.5'))
         self.assertEqual(f.max_value, 1.5)
@@ -371,52 +397,50 @@ class FieldsTests(SimpleTestCase):
     def test_decimalfield_1(self):
         f = DecimalField(max_digits=4, decimal_places=2)
         self.assertWidgetRendersTo(f, '<input id="id_f" step="0.01" type="number" name="f" />')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual(f.clean('1'), Decimal("1"))
         self.assertIsInstance(f.clean('1'), Decimal)
         self.assertEqual(f.clean('23'), Decimal("23"))
         self.assertEqual(f.clean('3.14'), Decimal("3.14"))
         self.assertEqual(f.clean(3.14), Decimal("3.14"))
         self.assertEqual(f.clean(Decimal('3.14')), Decimal("3.14"))
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, 'NaN')
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, 'Inf')
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, '-Inf')
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, 'a')
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, 'łąść')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('NaN')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('Inf')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('-Inf')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('łąść')
         self.assertEqual(f.clean('1.0 '), Decimal("1.0"))
         self.assertEqual(f.clean(' 1.0'), Decimal("1.0"))
         self.assertEqual(f.clean(' 1.0 '), Decimal("1.0"))
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, '1.0a')
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 4 digits in total.'",
-            f.clean, '123.45'
-        )
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 2 decimal places.'",
-            f.clean, '1.234'
-        )
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 2 digits before the decimal point.'",
-            f.clean, '123.4'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('1.0a')
+        with self.assertRaisesMessage(ValidationError, "'Ensure that there are no more than 4 digits in total.'"):
+            f.clean('123.45')
+        with self.assertRaisesMessage(ValidationError, "'Ensure that there are no more than 2 decimal places.'"):
+            f.clean('1.234')
+        msg = "'Ensure that there are no more than 2 digits before the decimal point.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('123.4')
         self.assertEqual(f.clean('-12.34'), Decimal("-12.34"))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 4 digits in total.'",
-            f.clean, '-123.45'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure that there are no more than 4 digits in total.'"):
+            f.clean('-123.45')
         self.assertEqual(f.clean('-.12'), Decimal("-0.12"))
         self.assertEqual(f.clean('-00.12'), Decimal("-0.12"))
         self.assertEqual(f.clean('-000.12'), Decimal("-0.12"))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 2 decimal places.'",
-            f.clean, '-000.123'
-        )
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 4 digits in total.'",
-            f.clean, '-000.12345'
-        )
-        self.assertRaisesMessage(ValidationError, "'Enter a number.'", f.clean, '--0.12')
+        with self.assertRaisesMessage(ValidationError, "'Ensure that there are no more than 2 decimal places.'"):
+            f.clean('-000.123')
+        with self.assertRaisesMessage(ValidationError, "'Ensure that there are no more than 4 digits in total.'"):
+            f.clean('-000.12345')
+        with self.assertRaisesMessage(ValidationError, "'Enter a number.'"):
+            f.clean('--0.12')
         self.assertEqual(f.max_digits, 4)
         self.assertEqual(f.decimal_places, 2)
         self.assertEqual(f.max_value, None)
@@ -435,11 +459,10 @@ class FieldsTests(SimpleTestCase):
     def test_decimalfield_3(self):
         f = DecimalField(max_digits=4, decimal_places=2, max_value=Decimal('1.5'), min_value=Decimal('0.5'))
         self.assertWidgetRendersTo(f, '<input step="0.01" name="f" min="0.5" max="1.5" type="number" id="id_f" />')
-        self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 1.5.'", f.clean, '1.6')
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value is greater than or equal to 0.5.'",
-            f.clean, '0.4'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is less than or equal to 1.5.'"):
+            f.clean('1.6')
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value is greater than or equal to 0.5.'"):
+            f.clean('0.4')
         self.assertEqual(f.clean('1.5'), Decimal("1.5"))
         self.assertEqual(f.clean('0.5'), Decimal("0.5"))
         self.assertEqual(f.clean('.5'), Decimal("0.5"))
@@ -451,10 +474,8 @@ class FieldsTests(SimpleTestCase):
 
     def test_decimalfield_4(self):
         f = DecimalField(decimal_places=2)
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 2 decimal places.'",
-            f.clean, '0.00000001'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure that there are no more than 2 decimal places.'"):
+            f.clean('0.00000001')
 
     def test_decimalfield_5(self):
         f = DecimalField(max_digits=3)
@@ -464,19 +485,16 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(f.clean('0000000.100'), Decimal("0.100"))
         # Only leading whole zeros "collapse" to one digit.
         self.assertEqual(f.clean('000000.02'), Decimal('0.02'))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 3 digits in total.'",
-            f.clean, '000000.0002'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure that there are no more than 3 digits in total.'"):
+            f.clean('000000.0002')
         self.assertEqual(f.clean('.002'), Decimal("0.002"))
 
     def test_decimalfield_6(self):
         f = DecimalField(max_digits=2, decimal_places=2)
         self.assertEqual(f.clean('.01'), Decimal(".01"))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure that there are no more than 0 digits before the decimal point.'",
-            f.clean, '1.1'
-        )
+        msg = "'Ensure that there are no more than 0 digits before the decimal point.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('1.1')
 
     def test_decimalfield_scientific(self):
         f = DecimalField(max_digits=2, decimal_places=2)
@@ -533,10 +551,14 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(datetime.date(2006, 10, 25), f.clean('October 25, 2006'))
         self.assertEqual(datetime.date(2006, 10, 25), f.clean('25 October 2006'))
         self.assertEqual(datetime.date(2006, 10, 25), f.clean('25 October, 2006'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, '2006-4-31')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, '200a-10-25')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, '25/10/06')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean('2006-4-31')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean('200a-10-25')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean('25/10/06')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
 
     def test_datefield_2(self):
         f = DateField(required=False)
@@ -550,9 +572,12 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(datetime.date(2006, 10, 25), f.clean(datetime.date(2006, 10, 25)))
         self.assertEqual(datetime.date(2006, 10, 25), f.clean(datetime.datetime(2006, 10, 25, 14, 30)))
         self.assertEqual(datetime.date(2006, 10, 25), f.clean('2006 10 25'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, '2006-10-25')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, '10/25/2006')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, '10/25/06')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean('2006-10-25')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean('10/25/2006')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean('10/25/06')
 
     def test_datefield_4(self):
         # Test whitespace stripping behavior (#5714)
@@ -563,12 +588,14 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(datetime.date(2006, 10, 25), f.clean(' October  25 2006 '))
         self.assertEqual(datetime.date(2006, 10, 25), f.clean(' October 25, 2006 '))
         self.assertEqual(datetime.date(2006, 10, 25), f.clean(' 25 October 2006 '))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, '   ')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean('   ')
 
     def test_datefield_5(self):
         # Test null bytes (#18982)
         f = DateField()
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, 'a\x00b')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean('a\x00b')
 
     def test_datefield_changed(self):
         format = '%d/%m/%Y'
@@ -594,8 +621,10 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(datetime.time(14, 25, 59), f.clean(datetime.time(14, 25, 59)))
         self.assertEqual(datetime.time(14, 25), f.clean('14:25'))
         self.assertEqual(datetime.time(14, 25, 59), f.clean('14:25:59'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid time.'", f.clean, 'hello')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid time.'", f.clean, '1:24 p.m.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid time.'"):
+            f.clean('hello')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid time.'"):
+            f.clean('1:24 p.m.')
 
     def test_timefield_2(self):
         f = TimeField(input_formats=['%I:%M %p'])
@@ -603,14 +632,16 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(datetime.time(14, 25, 59), f.clean(datetime.time(14, 25, 59)))
         self.assertEqual(datetime.time(4, 25), f.clean('4:25 AM'))
         self.assertEqual(datetime.time(16, 25), f.clean('4:25 PM'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid time.'", f.clean, '14:30:45')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid time.'"):
+            f.clean('14:30:45')
 
     def test_timefield_3(self):
         f = TimeField()
         # Test whitespace stripping behavior (#5714)
         self.assertEqual(datetime.time(14, 25), f.clean(' 14:25 '))
         self.assertEqual(datetime.time(14, 25, 59), f.clean(' 14:25:59 '))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid time.'", f.clean, '   ')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid time.'"):
+            f.clean('   ')
 
     def test_timefield_changed(self):
         t1 = datetime.time(12, 51, 34, 482548)
@@ -650,8 +681,10 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(datetime.datetime(2006, 10, 25, 14, 30), f.clean('10/25/06 14:30:00'))
         self.assertEqual(datetime.datetime(2006, 10, 25, 14, 30), f.clean('10/25/06 14:30'))
         self.assertEqual(datetime.datetime(2006, 10, 25, 0, 0), f.clean('10/25/06'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date/time.'", f.clean, 'hello')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date/time.'", f.clean, '2006-10-25 4:30 p.m.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date/time.'"):
+            f.clean('hello')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date/time.'"):
+            f.clean('2006-10-25 4:30 p.m.')
 
     def test_datetimefield_2(self):
         f = DateTimeField(input_formats=['%Y %m %d %I:%M %p'])
@@ -666,7 +699,8 @@ class FieldsTests(SimpleTestCase):
             f.clean(datetime.datetime(2006, 10, 25, 14, 30, 59, 200))
         )
         self.assertEqual(datetime.datetime(2006, 10, 25, 14, 30), f.clean('2006 10 25 2:30 PM'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date/time.'", f.clean, '2006-10-25 14:30:45')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date/time.'"):
+            f.clean('2006-10-25 14:30:45')
 
     def test_datetimefield_3(self):
         f = DateTimeField(required=False)
@@ -685,7 +719,8 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(datetime.datetime(2006, 10, 25, 0, 0), f.clean(' 10/25/2006 '))
         self.assertEqual(datetime.datetime(2006, 10, 25, 14, 30, 45), f.clean(' 10/25/06 14:30:45 '))
         self.assertEqual(datetime.datetime(2006, 10, 25, 0, 0), f.clean(' 10/25/06 '))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date/time.'", f.clean, '   ')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date/time.'"):
+            f.clean('   ')
 
     def test_datetimefield_5(self):
         f = DateTimeField(input_formats=['%Y.%m.%d %H:%M:%S.%f'])
@@ -742,32 +777,38 @@ class FieldsTests(SimpleTestCase):
         f = RegexField('^[0-9][A-F][0-9]$')
         self.assertEqual('2A2', f.clean('2A2'))
         self.assertEqual('3F3', f.clean('3F3'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, '3G3')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, ' 2A2')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, '2A2 ')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean('3G3')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean(' 2A2')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean('2A2 ')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
 
     def test_regexfield_2(self):
         f = RegexField('^[0-9][A-F][0-9]$', required=False)
         self.assertEqual('2A2', f.clean('2A2'))
         self.assertEqual('3F3', f.clean('3F3'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, '3G3')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean('3G3')
         self.assertEqual('', f.clean(''))
 
     def test_regexfield_3(self):
         f = RegexField(re.compile('^[0-9][A-F][0-9]$'))
         self.assertEqual('2A2', f.clean('2A2'))
         self.assertEqual('3F3', f.clean('3F3'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, '3G3')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, ' 2A2')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, '2A2 ')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean('3G3')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean(' 2A2')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean('2A2 ')
 
     def test_regexfield_5(self):
         f = RegexField('^[0-9]+$', min_length=5, max_length=10)
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value has at least 5 characters (it has 3).'",
-            f.clean, '123'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value has at least 5 characters (it has 3).'"):
+            f.clean('123')
         six.assertRaisesRegex(
             self, ValidationError,
             "'Ensure this value has at least 5 characters \(it has 3\)\.',"
@@ -776,11 +817,10 @@ class FieldsTests(SimpleTestCase):
         )
         self.assertEqual('12345', f.clean('12345'))
         self.assertEqual('1234567890', f.clean('1234567890'))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value has at most 10 characters (it has 11).'",
-            f.clean, '12345678901'
-        )
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, '12345a')
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value has at most 10 characters (it has 11).'"):
+            f.clean('12345678901')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean('12345a')
 
     def test_regexfield_6(self):
         """
@@ -794,7 +834,8 @@ class FieldsTests(SimpleTestCase):
         f = RegexField('^[a-z]+$')
         f.regex = '^[0-9]+$'
         self.assertEqual('1234', f.clean('1234'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid value.'", f.clean, 'abcd')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid value.'"):
+            f.clean('abcd')
 
     # EmailField ##################################################################
     # See also validators tests for validate_email specific tests
@@ -802,10 +843,13 @@ class FieldsTests(SimpleTestCase):
     def test_emailfield_1(self):
         f = EmailField()
         self.assertWidgetRendersTo(f, '<input type="email" name="f" id="id_f" />')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual('person@example.com', f.clean('person@example.com'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid email address.'", f.clean, 'foo')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid email address.'"):
+            f.clean('foo')
         self.assertEqual('local@domain.with.idn.xyz\xe4\xf6\xfc\xdfabc.part.com',
             f.clean('local@domain.with.idn.xyzäöüßabc.part.com'))
 
@@ -822,52 +866,44 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual('', f.clean(None))
         self.assertEqual('person@example.com', f.clean('person@example.com'))
         self.assertEqual('example@example.com', f.clean('      example@example.com  \t   \t '))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid email address.'", f.clean, 'foo')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid email address.'"):
+            f.clean('foo')
 
     def test_emailfield_min_max_length(self):
         f = EmailField(min_length=10, max_length=15)
         self.assertWidgetRendersTo(f, '<input id="id_f" type="email" name="f" maxlength="15" />')
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value has at least 10 characters (it has 9).'",
-            f.clean, 'a@foo.com'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value has at least 10 characters (it has 9).'"):
+            f.clean('a@foo.com')
         self.assertEqual('alf@foo.com', f.clean('alf@foo.com'))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value has at most 15 characters (it has 20).'",
-            f.clean, 'alf123456788@foo.com'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value has at most 15 characters (it has 20).'"):
+            f.clean('alf123456788@foo.com')
 
     # FileField ##################################################################
 
     def test_filefield_1(self):
         f = FileField()
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '', '')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('', '')
         self.assertEqual('files/test1.pdf', f.clean('', 'files/test1.pdf'))
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None, '')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None, '')
         self.assertEqual('files/test2.pdf', f.clean(None, 'files/test2.pdf'))
-        self.assertRaisesMessage(
-            ValidationError, "'No file was submitted. Check the encoding type on the form.'",
-            f.clean, SimpleUploadedFile('', b'')
-        )
-        self.assertRaisesMessage(
-            ValidationError, "'No file was submitted. Check the encoding type on the form.'",
-            f.clean, SimpleUploadedFile('', b''), ''
-        )
+        no_file_msg = "'No file was submitted. Check the encoding type on the form.'"
+        with self.assertRaisesMessage(ValidationError, no_file_msg):
+            f.clean(SimpleUploadedFile('', b''))
+        with self.assertRaisesMessage(ValidationError, no_file_msg):
+            f.clean(SimpleUploadedFile('', b''), '')
         self.assertEqual('files/test3.pdf', f.clean(None, 'files/test3.pdf'))
-        self.assertRaisesMessage(
-            ValidationError, "'No file was submitted. Check the encoding type on the form.'",
-            f.clean, 'some content that is not a file'
-        )
-        self.assertRaisesMessage(
-            ValidationError, "'The submitted file is empty.'",
-            f.clean, SimpleUploadedFile('name', None)
-        )
-        self.assertRaisesMessage(
-            ValidationError, "'The submitted file is empty.'",
-            f.clean, SimpleUploadedFile('name', b'')
-        )
+        with self.assertRaisesMessage(ValidationError, no_file_msg):
+            f.clean('some content that is not a file')
+        with self.assertRaisesMessage(ValidationError, "'The submitted file is empty.'"):
+            f.clean(SimpleUploadedFile('name', None))
+        with self.assertRaisesMessage(ValidationError, "'The submitted file is empty.'"):
+            f.clean(SimpleUploadedFile('name', b''))
         self.assertEqual(SimpleUploadedFile, type(f.clean(SimpleUploadedFile('name', b'Some File Content'))))
         self.assertIsInstance(
             f.clean(SimpleUploadedFile('我隻氣墊船裝滿晒鱔.txt', 'मेरी मँडराने वाली नाव सर्पमीनों से भरी ह'.encode('utf-8'))),
@@ -880,10 +916,8 @@ class FieldsTests(SimpleTestCase):
 
     def test_filefield_2(self):
         f = FileField(max_length=5)
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this filename has at most 5 characters (it has 18).'",
-            f.clean, SimpleUploadedFile('test_maxlength.txt', b'hello world')
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure this filename has at most 5 characters (it has 18).'"):
+            f.clean(SimpleUploadedFile('test_maxlength.txt', b'hello world'))
         self.assertEqual('files/test1.pdf', f.clean('', 'files/test1.pdf'))
         self.assertEqual('files/test2.pdf', f.clean(None, 'files/test2.pdf'))
         self.assertEqual(SimpleUploadedFile, type(f.clean(SimpleUploadedFile('name', b'Some File Content'))))
@@ -962,8 +996,10 @@ class FieldsTests(SimpleTestCase):
     def test_urlfield_1(self):
         f = URLField()
         self.assertWidgetRendersTo(f, '<input type="url" name="f" id="id_f" />')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual('http://localhost', f.clean('http://localhost'))
         self.assertEqual('http://example.com', f.clean('http://example.com'))
         self.assertEqual('http://example.com.', f.clean('http://example.com.'))
@@ -973,17 +1009,28 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual('http://subdomain.domain.com', f.clean('subdomain.domain.com'))
         self.assertEqual('http://200.8.9.10', f.clean('http://200.8.9.10'))
         self.assertEqual('http://200.8.9.10:8000/test', f.clean('http://200.8.9.10:8000/test'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'foo')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://example')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://example.')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'com.')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, '.')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://.com')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://invalid-.com')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://-invalid.com')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://inv-.alid-.com')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://inv-.-alid.com')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('foo')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://example')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://example.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('com.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://.com')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://invalid-.com')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://-invalid.com')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://inv-.alid-.com')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://inv-.-alid.com')
         self.assertEqual('http://valid-----hyphens.com', f.clean('http://valid-----hyphens.com'))
         self.assertEqual(
             'http://some.idn.xyz\xe4\xf6\xfc\xdfabc.domain.com:123/blah',
@@ -993,17 +1040,21 @@ class FieldsTests(SimpleTestCase):
             'http://www.example.com/s/http://code.djangoproject.com/ticket/13804',
             f.clean('www.example.com/s/http://code.djangoproject.com/ticket/13804')
         )
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, '[a')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://[a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('[a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://[a')
 
     def test_url_regex_ticket11198(self):
         f = URLField()
         # hangs "forever" if catastrophic backtracking in ticket:#11198 not fixed
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://%s' % ("X" * 200,))
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://%s' % ("X" * 200,))
 
         # a second test, to make sure the problem is really addressed, even on
         # domains that don't fail the domain label length check in the regex
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://%s' % ("X" * 60,))
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://%s' % ("X" * 60,))
 
     def test_urlfield_2(self):
         f = URLField(required=False)
@@ -1011,24 +1062,25 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual('', f.clean(None))
         self.assertEqual('http://example.com', f.clean('http://example.com'))
         self.assertEqual('http://www.example.com', f.clean('http://www.example.com'))
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'foo')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://example')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://example.')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 'http://.com')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('foo')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://example')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://example.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean('http://.com')
 
     def test_urlfield_5(self):
         f = URLField(min_length=15, max_length=20)
         self.assertWidgetRendersTo(f, '<input id="id_f" type="url" name="f" maxlength="20" />')
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value has at least 15 characters (it has 12).'",
-            f.clean, 'http://f.com'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value has at least 15 characters (it has 12).'"):
+            f.clean('http://f.com')
         self.assertEqual('http://example.com', f.clean('http://example.com'))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value has at most 20 characters (it has 37).'",
-            f.clean, 'http://abcdefghijklmnopqrstuvwxyz.com'
-        )
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value has at most 20 characters (it has 37).'"):
+            f.clean('http://abcdefghijklmnopqrstuvwxyz.com')
 
     def test_urlfield_6(self):
         f = URLField(required=False)
@@ -1075,7 +1127,8 @@ class FieldsTests(SimpleTestCase):
 
     def test_urlfield_not_string(self):
         f = URLField(required=False)
-        self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'", f.clean, 23)
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid URL.'"):
+            f.clean(23)
 
     def test_urlfield_normalization(self):
         f = URLField()
@@ -1085,15 +1138,20 @@ class FieldsTests(SimpleTestCase):
 
     def test_booleanfield_1(self):
         f = BooleanField()
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual(True, f.clean(True))
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, False)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(False)
         self.assertEqual(True, f.clean(1))
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, 0)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(0)
         self.assertEqual(True, f.clean('Django rocks'))
         self.assertEqual(True, f.clean('True'))
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, 'False')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('False')
 
     def test_booleanfield_2(self):
         f = BooleanField(required=False)
@@ -1129,14 +1187,15 @@ class FieldsTests(SimpleTestCase):
 
     def test_choicefield_1(self):
         f = ChoiceField(choices=[('1', 'One'), ('2', 'Two')])
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual('1', f.clean(1))
         self.assertEqual('1', f.clean('1'))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 3 is not one of the available choices.'",
-            f.clean, '3'
-        )
+        msg = "'Select a valid choice. 3 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('3')
 
     def test_choicefield_2(self):
         f = ChoiceField(choices=[('1', 'One'), ('2', 'Two')], required=False)
@@ -1144,18 +1203,16 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual('', f.clean(None))
         self.assertEqual('1', f.clean(1))
         self.assertEqual('1', f.clean('1'))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 3 is not one of the available choices.'",
-            f.clean, '3'
-        )
+        msg = "'Select a valid choice. 3 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('3')
 
     def test_choicefield_3(self):
         f = ChoiceField(choices=[('J', 'John'), ('P', 'Paul')])
         self.assertEqual('J', f.clean('J'))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. John is not one of the available choices.'",
-            f.clean, 'John'
-        )
+        msg = "'Select a valid choice. John is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('John')
 
     def test_choicefield_4(self):
         f = ChoiceField(
@@ -1170,10 +1227,9 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual('3', f.clean('3'))
         self.assertEqual('5', f.clean(5))
         self.assertEqual('5', f.clean('5'))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 6 is not one of the available choices.'",
-            f.clean, '6'
-        )
+        msg = "'Select a valid choice. 6 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('6')
 
     def test_choicefield_callable(self):
         def choices():
@@ -1211,10 +1267,9 @@ class FieldsTests(SimpleTestCase):
     def test_typedchoicefield_1(self):
         f = TypedChoiceField(choices=[(1, "+1"), (-1, "-1")], coerce=int)
         self.assertEqual(1, f.clean('1'))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 2 is not one of the available choices.'",
-            f.clean, '2'
-        )
+        msg = "'Select a valid choice. 2 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('2')
 
     def test_typedchoicefield_2(self):
         # Different coercion, same validation.
@@ -1230,12 +1285,12 @@ class FieldsTests(SimpleTestCase):
         # Even more weirdness: if you have a valid choice but your coercion function
         # can't coerce, you'll still get a validation error. Don't do this!
         f = TypedChoiceField(choices=[('A', 'A'), ('B', 'B')], coerce=int)
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. B is not one of the available choices.'",
-            f.clean, 'B'
-        )
+        msg = "'Select a valid choice. B is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('B')
         # Required fields require values
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
 
     def test_typedchoicefield_5(self):
         # Non-required fields aren't required
@@ -1272,14 +1327,11 @@ class FieldsTests(SimpleTestCase):
 
         f = TypedChoiceField(choices=[(1, "1"), (2, "2")], coerce=coerce_func, required=True)
         self.assertEqual(Decimal('1.2'), f.clean('2'))
-        self.assertRaisesMessage(
-            ValidationError, "'This field is required.'",
-            f.clean, ''
-        )
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 3 is not one of the available choices.'",
-            f.clean, '3'
-        )
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        msg = "'Select a valid choice. 3 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('3')
 
     # NullBooleanField ############################################################
 
@@ -1347,20 +1399,24 @@ class FieldsTests(SimpleTestCase):
 
     def test_multiplechoicefield_1(self):
         f = MultipleChoiceField(choices=[('1', 'One'), ('2', 'Two')])
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual(['1'], f.clean([1]))
         self.assertEqual(['1'], f.clean(['1']))
         self.assertEqual(['1', '2'], f.clean(['1', '2']))
         self.assertEqual(['1', '2'], f.clean([1, '2']))
         self.assertEqual(['1', '2'], f.clean((1, '2')))
-        self.assertRaisesMessage(ValidationError, "'Enter a list of values.'", f.clean, 'hello')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, [])
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, ())
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 3 is not one of the available choices.'",
-            f.clean, ['3']
-        )
+        with self.assertRaisesMessage(ValidationError, "'Enter a list of values.'"):
+            f.clean('hello')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean([])
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(())
+        msg = "'Select a valid choice. 3 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(['3'])
 
     def test_multiplechoicefield_2(self):
         f = MultipleChoiceField(choices=[('1', 'One'), ('2', 'Two')], required=False)
@@ -1371,13 +1427,13 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(['1', '2'], f.clean(['1', '2']))
         self.assertEqual(['1', '2'], f.clean([1, '2']))
         self.assertEqual(['1', '2'], f.clean((1, '2')))
-        self.assertRaisesMessage(ValidationError, "'Enter a list of values.'", f.clean, 'hello')
+        with self.assertRaisesMessage(ValidationError, "'Enter a list of values.'"):
+            f.clean('hello')
         self.assertEqual([], f.clean([]))
         self.assertEqual([], f.clean(()))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 3 is not one of the available choices.'",
-            f.clean, ['3']
-        )
+        with self.assertRaisesMessage(ValidationError,
+                "'Select a valid choice. 3 is not one of the available choices.'"):
+            f.clean(['3'])
 
     def test_multiplechoicefield_3(self):
         f = MultipleChoiceField(
@@ -1389,14 +1445,12 @@ class FieldsTests(SimpleTestCase):
         self.assertEqual(['1', '5'], f.clean([1, '5']))
         self.assertEqual(['1', '5'], f.clean(['1', 5]))
         self.assertEqual(['1', '5'], f.clean(['1', '5']))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 6 is not one of the available choices.'",
-            f.clean, ['6']
-        )
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 6 is not one of the available choices.'",
-            f.clean, ['1', '6']
-        )
+        msg = "'Select a valid choice. 6 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(['6'])
+        msg = "'Select a valid choice. 6 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(['1', '6'])
 
     def test_multiplechoicefield_changed(self):
         f = MultipleChoiceField(choices=[('1', 'One'), ('2', 'Two'), ('3', 'Three')])
@@ -1415,10 +1469,9 @@ class FieldsTests(SimpleTestCase):
     def test_typedmultiplechoicefield_1(self):
         f = TypedMultipleChoiceField(choices=[(1, "+1"), (-1, "-1")], coerce=int)
         self.assertEqual([1], f.clean(['1']))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 2 is not one of the available choices.'",
-            f.clean, ['2']
-        )
+        msg = "'Select a valid choice. 2 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(['2'])
 
     def test_typedmultiplechoicefield_2(self):
         # Different coercion, same validation.
@@ -1433,21 +1486,20 @@ class FieldsTests(SimpleTestCase):
     def test_typedmultiplechoicefield_4(self):
         f = TypedMultipleChoiceField(choices=[(1, "+1"), (-1, "-1")], coerce=int)
         self.assertEqual([1, -1], f.clean(['1', '-1']))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. 2 is not one of the available choices.'",
-            f.clean, ['1', '2']
-        )
+        msg = "'Select a valid choice. 2 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(['1', '2'])
 
     def test_typedmultiplechoicefield_5(self):
         # Even more weirdness: if you have a valid choice but your coercion function
         # can't coerce, you'll still get a validation error. Don't do this!
         f = TypedMultipleChoiceField(choices=[('A', 'A'), ('B', 'B')], coerce=int)
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. B is not one of the available choices.'",
-            f.clean, ['B']
-        )
+        msg = "'Select a valid choice. B is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(['B'])
         # Required fields require values
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, [])
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean([])
 
     def test_typedmultiplechoicefield_6(self):
         # Non-required fields aren't required
@@ -1475,33 +1527,33 @@ class FieldsTests(SimpleTestCase):
         f = TypedMultipleChoiceField(
             choices=[(1, "1"), (2, "2")], coerce=coerce_func, required=True)
         self.assertEqual([Decimal('1.2')], f.clean(['2']))
-        self.assertRaisesMessage(ValidationError,
-            "'This field is required.'", f.clean, [])
-        self.assertRaisesMessage(ValidationError,
-            "'Select a valid choice. 3 is not one of the available choices.'",
-            f.clean, ['3'])
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean([])
+        msg = "'Select a valid choice. 3 is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(['3'])
 
     # ComboField ##################################################################
 
     def test_combofield_1(self):
         f = ComboField(fields=[CharField(max_length=20), EmailField()])
         self.assertEqual('test@example.com', f.clean('test@example.com'))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value has at most 20 characters (it has 28).'",
-            f.clean, 'longemailaddress@example.com'
-        )
-        self.assertRaisesMessage(ValidationError, "'Enter a valid email address.'", f.clean, 'not an email')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value has at most 20 characters (it has 28).'"):
+            f.clean('longemailaddress@example.com')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid email address.'"):
+            f.clean('not an email')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
 
     def test_combofield_2(self):
         f = ComboField(fields=[CharField(max_length=20), EmailField()], required=False)
         self.assertEqual('test@example.com', f.clean('test@example.com'))
-        self.assertRaisesMessage(
-            ValidationError, "'Ensure this value has at most 20 characters (it has 28).'",
-            f.clean, 'longemailaddress@example.com'
-        )
-        self.assertRaisesMessage(ValidationError, "'Enter a valid email address.'", f.clean, 'not an email')
+        with self.assertRaisesMessage(ValidationError, "'Ensure this value has at most 20 characters (it has 28).'"):
+            f.clean('longemailaddress@example.com')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid email address.'"):
+            f.clean('not an email')
         self.assertEqual('', f.clean(''))
         self.assertEqual('', f.clean(None))
 
@@ -1531,10 +1583,9 @@ class FieldsTests(SimpleTestCase):
         for exp, got in zip(expected, fix_os_paths(f.choices)):
             self.assertEqual(exp[1], got[1])
             self.assertTrue(got[0].endswith(exp[0]))
-        self.assertRaisesMessage(
-            ValidationError, "'Select a valid choice. fields.py is not one of the available choices.'",
-            f.clean, 'fields.py'
-        )
+        msg = "'Select a valid choice. fields.py is not one of the available choices.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean('fields.py')
         assert fix_os_paths(f.clean(path + 'fields.py')).endswith('/django/forms/fields.py')
 
     def test_filepathfield_3(self):
@@ -1615,15 +1666,20 @@ class FieldsTests(SimpleTestCase):
             datetime.datetime(2006, 1, 10, 7, 30),
             f.clean([datetime.date(2006, 1, 10), datetime.time(7, 30)])
         )
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'Enter a list of values.'", f.clean, 'hello')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'Enter a list of values.'"):
+            f.clean('hello')
         six.assertRaisesRegex(
             self, ValidationError, "'Enter a valid date\.', u?'Enter a valid time\.'",
             f.clean, ['hello', 'there']
         )
-        self.assertRaisesMessage(ValidationError, "'Enter a valid time.'", f.clean, ['2006-01-10', 'there'])
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, ['hello', '07:30'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid time.'"):
+            f.clean(['2006-01-10', 'there'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean(['hello', '07:30'])
 
     def test_splitdatetimefield_2(self):
         f = SplitDateTimeField(required=False)
@@ -1636,16 +1692,22 @@ class FieldsTests(SimpleTestCase):
         self.assertIsNone(f.clean(''))
         self.assertIsNone(f.clean(['']))
         self.assertIsNone(f.clean(['', '']))
-        self.assertRaisesMessage(ValidationError, "'Enter a list of values.'", f.clean, 'hello')
+        with self.assertRaisesMessage(ValidationError, "'Enter a list of values.'"):
+            f.clean('hello')
         six.assertRaisesRegex(
             self, ValidationError, "'Enter a valid date\.', u?'Enter a valid time\.'",
             f.clean, ['hello', 'there']
         )
-        self.assertRaisesMessage(ValidationError, "'Enter a valid time.'", f.clean, ['2006-01-10', 'there'])
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, ['hello', '07:30'])
-        self.assertRaisesMessage(ValidationError, "'Enter a valid time.'", f.clean, ['2006-01-10', ''])
-        self.assertRaisesMessage(ValidationError, "'Enter a valid time.'", f.clean, ['2006-01-10'])
-        self.assertRaisesMessage(ValidationError, "'Enter a valid date.'", f.clean, ['', '07:30'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid time.'"):
+            f.clean(['2006-01-10', 'there'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean(['hello', '07:30'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid time.'"):
+            f.clean(['2006-01-10', ''])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid time.'"):
+            f.clean(['2006-01-10'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid date.'"):
+            f.clean(['', '07:30'])
 
     def test_splitdatetimefield_changed(self):
         f = SplitDateTimeField(input_date_formats=['%d/%m/%Y'])
@@ -1666,75 +1728,106 @@ class FieldsTests(SimpleTestCase):
         # The edge cases of the IPv6 validation code are not deeply tested
         # here, they are covered in the tests for django.utils.ipv6
         f = GenericIPAddressField()
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual(f.clean(' 127.0.0.1 '), '127.0.0.1')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'", f.clean, 'foo')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'", f.clean, '127.0.0.')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'", f.clean, '1.2.3.4.5')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'", f.clean, '256.125.1.5')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'"):
+            f.clean('foo')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'"):
+            f.clean('127.0.0.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'"):
+            f.clean('1.2.3.4.5')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'"):
+            f.clean('256.125.1.5')
         self.assertEqual(f.clean(' fe80::223:6cff:fe8a:2e8a '), 'fe80::223:6cff:fe8a:2e8a')
         self.assertEqual(f.clean(' 2a02::223:6cff:fe8a:2e8a '), '2a02::223:6cff:fe8a:2e8a')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '12345:2:3:4')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1::2:3::4')
-        self.assertRaisesMessage(
-            ValidationError, "'This is not a valid IPv6 address.'",
-            f.clean, 'foo::223:6cff:fe8a:2e8a'
-        )
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1::2:3:4:5:6:7:8')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1:2')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('12345:2:3:4')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1::2:3::4')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('foo::223:6cff:fe8a:2e8a')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1::2:3:4:5:6:7:8')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1:2')
 
     def test_generic_ipaddress_as_ipv4_only(self):
         f = GenericIPAddressField(protocol="IPv4")
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
         self.assertEqual(f.clean(' 127.0.0.1 '), '127.0.0.1')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'", f.clean, 'foo')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'", f.clean, '127.0.0.')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'", f.clean, '1.2.3.4.5')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'", f.clean, '256.125.1.5')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'", f.clean, 'fe80::223:6cff:fe8a:2e8a')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'", f.clean, '2a02::223:6cff:fe8a:2e8a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'"):
+            f.clean('foo')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'"):
+            f.clean('127.0.0.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'"):
+            f.clean('1.2.3.4.5')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'"):
+            f.clean('256.125.1.5')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'"):
+            f.clean('fe80::223:6cff:fe8a:2e8a')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 address.'"):
+            f.clean('2a02::223:6cff:fe8a:2e8a')
 
     def test_generic_ipaddress_as_ipv6_only(self):
         f = GenericIPAddressField(protocol="IPv6")
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'", f.clean, '127.0.0.1')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'", f.clean, 'foo')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'", f.clean, '127.0.0.')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'", f.clean, '1.2.3.4.5')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'", f.clean, '256.125.1.5')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'"):
+            f.clean('127.0.0.1')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'"):
+            f.clean('foo')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'"):
+            f.clean('127.0.0.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'"):
+            f.clean('1.2.3.4.5')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv6 address.'"):
+            f.clean('256.125.1.5')
         self.assertEqual(f.clean(' fe80::223:6cff:fe8a:2e8a '), 'fe80::223:6cff:fe8a:2e8a')
         self.assertEqual(f.clean(' 2a02::223:6cff:fe8a:2e8a '), '2a02::223:6cff:fe8a:2e8a')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '12345:2:3:4')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1::2:3::4')
-        self.assertRaisesMessage(
-            ValidationError, "'This is not a valid IPv6 address.'",
-            f.clean, 'foo::223:6cff:fe8a:2e8a'
-        )
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1::2:3:4:5:6:7:8')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1:2')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('12345:2:3:4')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1::2:3::4')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('foo::223:6cff:fe8a:2e8a')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1::2:3:4:5:6:7:8')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1:2')
 
     def test_generic_ipaddress_as_generic_not_required(self):
         f = GenericIPAddressField(required=False)
         self.assertEqual(f.clean(''), '')
         self.assertEqual(f.clean(None), '')
         self.assertEqual(f.clean('127.0.0.1'), '127.0.0.1')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'", f.clean, 'foo')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'", f.clean, '127.0.0.')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'", f.clean, '1.2.3.4.5')
-        self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'", f.clean, '256.125.1.5')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'"):
+            f.clean('foo')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'"):
+            f.clean('127.0.0.')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'"):
+            f.clean('1.2.3.4.5')
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid IPv4 or IPv6 address.'"):
+            f.clean('256.125.1.5')
         self.assertEqual(f.clean(' fe80::223:6cff:fe8a:2e8a '), 'fe80::223:6cff:fe8a:2e8a')
         self.assertEqual(f.clean(' 2a02::223:6cff:fe8a:2e8a '), '2a02::223:6cff:fe8a:2e8a')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '12345:2:3:4')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1::2:3::4')
-        self.assertRaisesMessage(
-            ValidationError, "'This is not a valid IPv6 address.'",
-            f.clean, 'foo::223:6cff:fe8a:2e8a'
-        )
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1::2:3:4:5:6:7:8')
-        self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'", f.clean, '1:2')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('12345:2:3:4')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1::2:3::4')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('foo::223:6cff:fe8a:2e8a')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1::2:3:4:5:6:7:8')
+        with self.assertRaisesMessage(ValidationError, "'This is not a valid IPv6 address.'"):
+            f.clean('1:2')
 
     def test_generic_ipaddress_normalization(self):
         # Test the normalizing code
diff --git a/tests/forms_tests/tests/test_forms.py b/tests/forms_tests/tests/test_forms.py
index 66b1737e6f..17703f2d23 100644
--- a/tests/forms_tests/tests/test_forms.py
+++ b/tests/forms_tests/tests/test_forms.py
@@ -2733,14 +2733,19 @@ Good luck picking a username that doesn&#39;t already exist.</p>
         # An empty value for any field will raise a `required` error on a
         # required `MultiValueField`.
         f = PhoneField()
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, [])
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, ['+61'])
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, ['+61', '287654321', '123'])
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean([])
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(['+61'])
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(['+61', '287654321', '123'])
         self.assertEqual('+61.287654321 ext. 123 (label: Home)', f.clean(['+61', '287654321', '123', 'Home']))
-        self.assertRaisesMessage(ValidationError,
-            "'Enter a valid country code.'", f.clean, ['61', '287654321', '123', 'Home'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid country code.'"):
+            f.clean(['61', '287654321', '123', 'Home'])
 
         # Empty values for fields will NOT raise a `required` error on an
         # optional `MultiValueField`
@@ -2751,23 +2756,27 @@ Good luck picking a username that doesn&#39;t already exist.</p>
         self.assertEqual('+61. ext.  (label: )', f.clean(['+61']))
         self.assertEqual('+61.287654321 ext. 123 (label: )', f.clean(['+61', '287654321', '123']))
         self.assertEqual('+61.287654321 ext. 123 (label: Home)', f.clean(['+61', '287654321', '123', 'Home']))
-        self.assertRaisesMessage(ValidationError,
-            "'Enter a valid country code.'", f.clean, ['61', '287654321', '123', 'Home'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid country code.'"):
+            f.clean(['61', '287654321', '123', 'Home'])
 
         # For a required `MultiValueField` with `require_all_fields=False`, a
         # `required` error will only be raised if all fields are empty. Fields
         # can individually be required or optional. An empty value for any
         # required field will raise an `incomplete` error.
         f = PhoneField(require_all_fields=False)
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, '')
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, None)
-        self.assertRaisesMessage(ValidationError, "'This field is required.'", f.clean, [])
-        self.assertRaisesMessage(ValidationError, "'Enter a complete value.'", f.clean, ['+61'])
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean('')
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean(None)
+        with self.assertRaisesMessage(ValidationError, "'This field is required.'"):
+            f.clean([])
+        with self.assertRaisesMessage(ValidationError, "'Enter a complete value.'"):
+            f.clean(['+61'])
         self.assertEqual('+61.287654321 ext. 123 (label: )', f.clean(['+61', '287654321', '123']))
         six.assertRaisesRegex(self, ValidationError,
             "'Enter a complete value\.', u?'Enter an extension\.'", f.clean, ['', '', '', 'Home'])
-        self.assertRaisesMessage(ValidationError,
-            "'Enter a valid country code.'", f.clean, ['61', '287654321', '123', 'Home'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid country code.'"):
+            f.clean(['61', '287654321', '123', 'Home'])
 
         # For an optional `MultiValueField` with `require_all_fields=False`, we
         # don't get any `required` error but we still get `incomplete` errors.
@@ -2775,12 +2784,13 @@ Good luck picking a username that doesn&#39;t already exist.</p>
         self.assertIsNone(f.clean(''))
         self.assertIsNone(f.clean(None))
         self.assertIsNone(f.clean([]))
-        self.assertRaisesMessage(ValidationError, "'Enter a complete value.'", f.clean, ['+61'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a complete value.'"):
+            f.clean(['+61'])
         self.assertEqual('+61.287654321 ext. 123 (label: )', f.clean(['+61', '287654321', '123']))
         six.assertRaisesRegex(self, ValidationError,
             "'Enter a complete value\.', u?'Enter an extension\.'", f.clean, ['', '', '', 'Home'])
-        self.assertRaisesMessage(ValidationError,
-            "'Enter a valid country code.'", f.clean, ['61', '287654321', '123', 'Home'])
+        with self.assertRaisesMessage(ValidationError, "'Enter a valid country code.'"):
+            f.clean(['61', '287654321', '123', 'Home'])
 
     def test_custom_empty_values(self):
         """
diff --git a/tests/forms_tests/widget_tests/test_selectdatewidget.py b/tests/forms_tests/widget_tests/test_selectdatewidget.py
index e95c083532..6efa240b66 100644
--- a/tests/forms_tests/widget_tests/test_selectdatewidget.py
+++ b/tests/forms_tests/widget_tests/test_selectdatewidget.py
@@ -384,8 +384,8 @@ class SelectDateWidgetTest(WidgetTest):
             """,
         )
 
-        self.assertRaisesMessage(ValueError, 'empty_label list/tuple must have 3 elements.',
-            SelectDateWidget, years=('2014',), empty_label=('not enough', 'values'))
+        with self.assertRaisesMessage(ValueError, 'empty_label list/tuple must have 3 elements.'):
+            SelectDateWidget(years=('2014',), empty_label=('not enough', 'values'))
 
     @override_settings(USE_L10N=True)
     @translation.override('nl')
diff --git a/tests/get_earliest_or_latest/tests.py b/tests/get_earliest_or_latest/tests.py
index d74a0724d7..e03f701da6 100644
--- a/tests/get_earliest_or_latest/tests.py
+++ b/tests/get_earliest_or_latest/tests.py
@@ -58,12 +58,12 @@ class EarliestOrLatestTests(TestCase):
         # Ensure that error is raised if the user forgot to add a get_latest_by
         # in the Model.Meta
         Article.objects.model._meta.get_latest_by = None
-        self.assertRaisesMessage(
+        with self.assertRaisesMessage(
             AssertionError,
             "earliest() and latest() require either a field_name parameter or "
-            "'get_latest_by' in the model",
-            lambda: Article.objects.earliest(),
-        )
+            "'get_latest_by' in the model"
+        ):
+            Article.objects.earliest()
 
     def test_latest(self):
         # Because no Articles exist yet, latest() raises ArticleDoesNotExist.
@@ -109,12 +109,11 @@ class EarliestOrLatestTests(TestCase):
         # Ensure that error is raised if the user forgot to add a get_latest_by
         # in the Model.Meta
         Article.objects.model._meta.get_latest_by = None
-        self.assertRaisesMessage(
+        with self.assertRaisesMessage(
             AssertionError,
-            "earliest() and latest() require either a field_name parameter or "
-            "'get_latest_by' in the model",
-            lambda: Article.objects.latest(),
-        )
+                "earliest() and latest() require either a field_name parameter or "
+                "'get_latest_by' in the model"):
+            Article.objects.latest()
 
     def test_latest_manual(self):
         # You can still use latest() with a model that doesn't have
diff --git a/tests/get_object_or_404/tests.py b/tests/get_object_or_404/tests.py
index 55d1de7c2c..ac4b2d4738 100644
--- a/tests/get_object_or_404/tests.py
+++ b/tests/get_object_or_404/tests.py
@@ -81,27 +81,18 @@ class GetObjectOr404Tests(TestCase):
     def test_bad_class(self):
         # Given an argument klass that is not a Model, Manager, or Queryset
         # raises a helpful ValueError message
-        self.assertRaisesMessage(
-            ValueError,
-            "Object is of type 'str', but must be a Django Model, Manager, "
-            "or QuerySet",
-            get_object_or_404, str("Article"), title__icontains="Run"
-        )
+        msg = "Object is of type 'str', but must be a Django Model, Manager, or QuerySet"
+        with self.assertRaisesMessage(ValueError, msg):
+            get_object_or_404(str("Article"), title__icontains="Run")
 
         class CustomClass(object):
             pass
 
-        self.assertRaisesMessage(
-            ValueError,
-            "Object is of type 'CustomClass', but must be a Django Model, "
-            "Manager, or QuerySet",
-            get_object_or_404, CustomClass, title__icontains="Run"
-        )
+        msg = "Object is of type 'CustomClass', but must be a Django Model, Manager, or QuerySet"
+        with self.assertRaisesMessage(ValueError, msg):
+            get_object_or_404(CustomClass, title__icontains="Run")
 
         # Works for lists too
-        self.assertRaisesMessage(
-            ValueError,
-            "Object is of type 'list', but must be a Django Model, Manager, "
-            "or QuerySet",
-            get_list_or_404, [Article], title__icontains="Run"
-        )
+        msg = "Object is of type 'list', but must be a Django Model, Manager, or QuerySet"
+        with self.assertRaisesMessage(ValueError, msg):
+            get_list_or_404([Article], title__icontains="Run")
diff --git a/tests/invalid_models_tests/test_relative_fields.py b/tests/invalid_models_tests/test_relative_fields.py
index c2895f681f..ba0354d5e1 100644
--- a/tests/invalid_models_tests/test_relative_fields.py
+++ b/tests/invalid_models_tests/test_relative_fields.py
@@ -1355,9 +1355,8 @@ class M2mThroughFieldsTests(SimpleTestCase):
         class Fan(models.Model):
             pass
 
-        self.assertRaisesMessage(
-            ValueError, 'Cannot specify through_fields without a through model',
-            models.ManyToManyField, Fan, through_fields=('f1', 'f2'))
+        with self.assertRaisesMessage(ValueError, 'Cannot specify through_fields without a through model'):
+            models.ManyToManyField(Fan, through_fields=('f1', 'f2'))
 
     def test_invalid_order(self):
         """
diff --git a/tests/mail/tests.py b/tests/mail/tests.py
index 58b6151efb..fe564ad765 100644
--- a/tests/mail/tests.py
+++ b/tests/mail/tests.py
@@ -1109,8 +1109,8 @@ class SMTPBackendTests(BaseEmailBackendTests, SMTPBackendTestsBase):
         backend = smtp.EmailBackend(
             username='not empty username', password='not empty password')
         try:
-            self.assertRaisesMessage(SMTPException,
-                'SMTP AUTH extension not supported by server.', backend.open)
+            with self.assertRaisesMessage(SMTPException, 'SMTP AUTH extension not supported by server.'):
+                backend.open()
         finally:
             backend.close()
 
@@ -1185,8 +1185,8 @@ class SMTPBackendTests(BaseEmailBackendTests, SMTPBackendTestsBase):
         backend = smtp.EmailBackend()
         self.assertTrue(backend.use_tls)
         try:
-            self.assertRaisesMessage(SMTPException,
-                'STARTTLS extension not supported by server.', backend.open)
+            with self.assertRaisesMessage(SMTPException, 'STARTTLS extension not supported by server.'):
+                backend.open()
         finally:
             backend.close()
 
diff --git a/tests/many_to_one/tests.py b/tests/many_to_one/tests.py
index 692a3e15e4..b3028e00ca 100644
--- a/tests/many_to_one/tests.py
+++ b/tests/many_to_one/tests.py
@@ -490,17 +490,12 @@ class ManyToOneTests(TestCase):
 
     def test_values_list_exception(self):
         expected_message = "Cannot resolve keyword 'notafield' into field. Choices are: %s"
-
-        self.assertRaisesMessage(FieldError,
-                                 expected_message % ', '.join(sorted(f.name for f in Reporter._meta.get_fields())),
-                                 Article.objects.values_list,
-                                 'reporter__notafield')
-        self.assertRaisesMessage(
-            FieldError,
-            expected_message % ', '.join(['EXTRA'] + sorted(f.name for f in Article._meta.get_fields())),
-            Article.objects.extra(select={'EXTRA': 'EXTRA_SELECT'}).values_list,
-            'notafield'
-        )
+        reporter_fields = ', '.join(sorted(f.name for f in Reporter._meta.get_fields()))
+        with self.assertRaisesMessage(FieldError, expected_message % reporter_fields):
+            Article.objects.values_list('reporter__notafield')
+        article_fields = ', '.join(['EXTRA'] + sorted(f.name for f in Article._meta.get_fields()))
+        with self.assertRaisesMessage(FieldError, expected_message % article_fields):
+            Article.objects.extra(select={'EXTRA': 'EXTRA_SELECT'}).values_list('notafield')
 
     def test_fk_assignment_and_related_object_cache(self):
         # Tests of ForeignKey assignment and the related-object cache (see #6886).
diff --git a/tests/model_fields/test_uuid.py b/tests/model_fields/test_uuid.py
index 5cded8d6af..050075444e 100644
--- a/tests/model_fields/test_uuid.py
+++ b/tests/model_fields/test_uuid.py
@@ -47,13 +47,11 @@ class TestSaveLoad(TestCase):
             PrimaryKeyUUIDModel.objects.get(pk=[])
 
     def test_wrong_value(self):
-        self.assertRaisesMessage(
-            ValueError, 'badly formed hexadecimal UUID string',
-            UUIDModel.objects.get, field='not-a-uuid')
+        with self.assertRaisesMessage(ValueError, 'badly formed hexadecimal UUID string'):
+            UUIDModel.objects.get(field='not-a-uuid')
 
-        self.assertRaisesMessage(
-            ValueError, 'badly formed hexadecimal UUID string',
-            UUIDModel.objects.create, field='not-a-uuid')
+        with self.assertRaisesMessage(ValueError, 'badly formed hexadecimal UUID string'):
+            UUIDModel.objects.create(field='not-a-uuid')
 
 
 class TestMigrations(SimpleTestCase):
diff --git a/tests/queries/tests.py b/tests/queries/tests.py
index b00b64027e..376208c62d 100644
--- a/tests/queries/tests.py
+++ b/tests/queries/tests.py
@@ -431,16 +431,10 @@ class Queries1Tests(BaseQuerysetTest):
     def test_heterogeneous_qs_combination(self):
         # Combining querysets built on different models should behave in a well-defined
         # fashion. We raise an error.
-        self.assertRaisesMessage(
-            AssertionError,
-            'Cannot combine queries on two different base models.',
-            lambda: Author.objects.all() & Tag.objects.all()
-        )
-        self.assertRaisesMessage(
-            AssertionError,
-            'Cannot combine queries on two different base models.',
-            lambda: Author.objects.all() | Tag.objects.all()
-        )
+        with self.assertRaisesMessage(AssertionError, 'Cannot combine queries on two different base models.'):
+            Author.objects.all() & Tag.objects.all()
+        with self.assertRaisesMessage(AssertionError, 'Cannot combine queries on two different base models.'):
+            Author.objects.all() | Tag.objects.all()
 
     def test_ticket3141(self):
         self.assertEqual(Author.objects.extra(select={'foo': '1'}).count(), 4)
@@ -759,11 +753,8 @@ class Queries1Tests(BaseQuerysetTest):
                 []
             )
             q.query.low_mark = 1
-            self.assertRaisesMessage(
-                AssertionError,
-                'Cannot change a query once a slice has been taken',
-                q.extra, select={'foo': "1"}
-            )
+            with self.assertRaisesMessage(AssertionError, 'Cannot change a query once a slice has been taken'):
+                q.extra(select={'foo': "1"})
             self.assertQuerysetEqual(q.reverse(), [])
             self.assertQuerysetEqual(q.defer('meal'), [])
             self.assertQuerysetEqual(q.only('meal'), [])
@@ -790,16 +781,10 @@ class Queries1Tests(BaseQuerysetTest):
         )
 
         # Multi-valued values() and values_list() querysets should raise errors.
-        self.assertRaisesMessage(
-            TypeError,
-            'Cannot use multi-field values as a filter value.',
-            lambda: Tag.objects.filter(name__in=Tag.objects.filter(parent=self.t1).values('name', 'id'))
-        )
-        self.assertRaisesMessage(
-            TypeError,
-            'Cannot use multi-field values as a filter value.',
-            lambda: Tag.objects.filter(name__in=Tag.objects.filter(parent=self.t1).values_list('name', 'id'))
-        )
+        with self.assertRaisesMessage(TypeError, 'Cannot use multi-field values as a filter value.'):
+            Tag.objects.filter(name__in=Tag.objects.filter(parent=self.t1).values('name', 'id'))
+        with self.assertRaisesMessage(TypeError, 'Cannot use multi-field values as a filter value.'):
+            Tag.objects.filter(name__in=Tag.objects.filter(parent=self.t1).values_list('name', 'id'))
 
     def test_ticket9985(self):
         # qs.values_list(...).values(...) combinations should work.
@@ -1329,11 +1314,8 @@ class Queries3Tests(BaseQuerysetTest):
     def test_ticket8683(self):
         # An error should be raised when QuerySet.datetimes() is passed the
         # wrong type of field.
-        self.assertRaisesMessage(
-            AssertionError,
-            "'name' isn't a DateTimeField.",
-            Item.objects.datetimes, 'name', 'month'
-        )
+        with self.assertRaisesMessage(AssertionError, "'name' isn't a DateTimeField."):
+            Item.objects.datetimes('name', 'month')
 
     def test_ticket22023(self):
         with self.assertRaisesMessage(TypeError,
@@ -2413,11 +2395,8 @@ class WeirdQuerysetSlicingTests(BaseQuerysetTest):
         self.assertQuerysetEqual(Article.objects.all()[0:0], [])
         self.assertQuerysetEqual(Article.objects.all()[0:0][:10], [])
         self.assertEqual(Article.objects.all()[:0].count(), 0)
-        self.assertRaisesMessage(
-            AssertionError,
-            'Cannot change a query once a slice has been taken.',
-            Article.objects.all()[:0].latest, 'created'
-        )
+        with self.assertRaisesMessage(AssertionError, 'Cannot change a query once a slice has been taken.'):
+            Article.objects.all()[:0].latest('created')
 
     def test_empty_resultset_sql(self):
         # ticket #12192
@@ -2528,16 +2507,10 @@ class ConditionalTests(BaseQuerysetTest):
     def test_infinite_loop(self):
         # If you're not careful, it's possible to introduce infinite loops via
         # default ordering on foreign keys in a cycle. We detect that.
-        self.assertRaisesMessage(
-            FieldError,
-            'Infinite loop caused by ordering.',
-            lambda: list(LoopX.objects.all())  # Force queryset evaluation with list()
-        )
-        self.assertRaisesMessage(
-            FieldError,
-            'Infinite loop caused by ordering.',
-            lambda: list(LoopZ.objects.all())  # Force queryset evaluation with list()
-        )
+        with self.assertRaisesMessage(FieldError, 'Infinite loop caused by ordering.'):
+            list(LoopX.objects.all())  # Force queryset evaluation with list()
+        with self.assertRaisesMessage(FieldError, 'Infinite loop caused by ordering.'):
+            list(LoopZ.objects.all())  # Force queryset evaluation with list()
 
         # Note that this doesn't cause an infinite loop, since the default
         # ordering on the Tag model is empty (and thus defaults to using "id"
diff --git a/tests/requests/tests.py b/tests/requests/tests.py
index 280320ae43..8113cb7685 100644
--- a/tests/requests/tests.py
+++ b/tests/requests/tests.py
@@ -772,11 +772,8 @@ class HostValidationTests(SimpleTestCase):
         ]:
             request = HttpRequest()
             request.META = {'HTTP_HOST': host}
-            self.assertRaisesMessage(
-                SuspiciousOperation,
-                msg_suggestion % (host, host),
-                request.get_host
-            )
+            with self.assertRaisesMessage(SuspiciousOperation, msg_suggestion % (host, host)):
+                request.get_host()
 
         for domain, port in [  # Valid-looking hosts with a port number
             ('example.com', 80),
@@ -786,28 +783,19 @@ class HostValidationTests(SimpleTestCase):
             host = '%s:%s' % (domain, port)
             request = HttpRequest()
             request.META = {'HTTP_HOST': host}
-            self.assertRaisesMessage(
-                SuspiciousOperation,
-                msg_suggestion % (host, domain),
-                request.get_host
-            )
+            with self.assertRaisesMessage(SuspiciousOperation, msg_suggestion % (host, domain)):
+                request.get_host()
 
         for host in self.poisoned_hosts:
             request = HttpRequest()
             request.META = {'HTTP_HOST': host}
-            self.assertRaisesMessage(
-                SuspiciousOperation,
-                msg_invalid_host % host,
-                request.get_host
-            )
+            with self.assertRaisesMessage(SuspiciousOperation, msg_invalid_host % host):
+                request.get_host()
 
         request = HttpRequest()
         request.META = {'HTTP_HOST': "invalid_hostname.com"}
-        self.assertRaisesMessage(
-            SuspiciousOperation,
-            msg_suggestion2 % "invalid_hostname.com",
-            request.get_host
-        )
+        with self.assertRaisesMessage(SuspiciousOperation, msg_suggestion2 % "invalid_hostname.com"):
+            request.get_host()
 
 
 class BuildAbsoluteURITestCase(SimpleTestCase):
diff --git a/tests/test_utils/tests.py b/tests/test_utils/tests.py
index fdc7a7e5dc..c4d51833f4 100644
--- a/tests/test_utils/tests.py
+++ b/tests/test_utils/tests.py
@@ -801,7 +801,8 @@ class AssertRaisesMsgTest(SimpleTestCase):
         """assertRaisesMessage shouldn't interpret RE special chars."""
         def func1():
             raise ValueError("[.*x+]y?")
-        self.assertRaisesMessage(ValueError, "[.*x+]y?", func1)
+        with self.assertRaisesMessage(ValueError, "[.*x+]y?"):
+            func1()
 
     @ignore_warnings(category=RemovedInDjango20Warning)
     def test_callable_obj_param(self):
diff --git a/tests/urlpatterns_reverse/tests.py b/tests/urlpatterns_reverse/tests.py
index b949cb0173..5c695df9f5 100644
--- a/tests/urlpatterns_reverse/tests.py
+++ b/tests/urlpatterns_reverse/tests.py
@@ -252,13 +252,13 @@ class NoURLPatternsTests(SimpleTestCase):
         """
         resolver = RegexURLResolver(r'^$', settings.ROOT_URLCONF)
 
-        self.assertRaisesMessage(
+        with self.assertRaisesMessage(
             ImproperlyConfigured,
             "The included URLconf 'urlpatterns_reverse.no_urls' does not "
             "appear to have any patterns in it. If you see valid patterns in "
-            "the file then the issue is probably caused by a circular import.",
-            getattr, resolver, 'url_patterns'
-        )
+            "the file then the issue is probably caused by a circular import."
+        ):
+            getattr(resolver, 'url_patterns')
 
 
 @override_settings(ROOT_URLCONF='urlpatterns_reverse.urls')
diff --git a/tests/utils_tests/test_datastructures.py b/tests/utils_tests/test_datastructures.py
index d151f12bb5..c90ef470bb 100644
--- a/tests/utils_tests/test_datastructures.py
+++ b/tests/utils_tests/test_datastructures.py
@@ -108,8 +108,8 @@ class ImmutableListTests(SimpleTestCase):
         d = ImmutableList(range(10))
 
         # AttributeError: ImmutableList object is immutable.
-        self.assertRaisesMessage(AttributeError,
-            'ImmutableList object is immutable.', d.sort)
+        with self.assertRaisesMessage(AttributeError, 'ImmutableList object is immutable.'):
+            d.sort()
 
         self.assertEqual(repr(d), '(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)')
 
@@ -119,8 +119,8 @@ class ImmutableListTests(SimpleTestCase):
         self.assertEqual(d[1], 1)
 
         # AttributeError: Object is immutable!
-        self.assertRaisesMessage(AttributeError,
-            'Object is immutable!', d.__setitem__, 1, 'test')
+        with self.assertRaisesMessage(AttributeError, 'Object is immutable!'):
+            d.__setitem__(1, 'test')
 
 
 class DictWrapperTests(SimpleTestCase):