Refs #33348 -- Improved messages raised by SimpleTestCase.assertFormError()/assertFormsetErrors().

This makes messages use BaseFormSet/BaseForm.__repr__() instead of
context, and adds the _assert_form_error() helper.

2 files changed, 83 insertions, 108 deletions

diff --git a/tests/test_client_regress/tests.py b/tests/test_client_regress/tests.py
index 11f63f8731..43cc9580cc 100644
--- a/tests/test_client_regress/tests.py
+++ b/tests/test_client_regress/tests.py
@@ -651,7 +651,11 @@ class AssertFormErrorTests(SimpleTestCase):
         self.assertEqual(response.status_code, 200)
         self.assertTemplateUsed(response, "Invalid POST Template")
 
-        msg = "The form 'form' in context 0 does not contain the field 'some_field'"
+        msg = (
+            "The form <TestForm bound=True, valid=False, "
+            "fields=(text;email;value;single;multi)> does not contain the field "
+            "'some_field'."
+        )
         with self.assertRaisesMessage(AssertionError, msg):
             self.assertFormError(response, "form", "some_field", "Some error.")
         with self.assertRaisesMessage(AssertionError, "abc: " + msg):
@@ -672,7 +676,10 @@ class AssertFormErrorTests(SimpleTestCase):
         self.assertEqual(response.status_code, 200)
         self.assertTemplateUsed(response, "Invalid POST Template")
 
-        msg = "The field 'value' on form 'form' in context 0 contains no errors"
+        msg = (
+            "The errors of field 'value' on form <TestForm bound=True, valid=False, "
+            "fields=(text;email;value;single;multi)> don't match."
+        )
         with self.assertRaisesMessage(AssertionError, msg):
             self.assertFormError(response, "form", "value", "Some error.")
         with self.assertRaisesMessage(AssertionError, "abc: " + msg):
@@ -694,9 +701,8 @@ class AssertFormErrorTests(SimpleTestCase):
         self.assertTemplateUsed(response, "Invalid POST Template")
 
         msg = (
-            "The field 'email' on form 'form' in context 0 does not contain "
-            "the error 'Some error.' (actual errors: ['Enter a valid email "
-            "address.'])"
+            "The errors of field 'email' on form <TestForm bound=True, valid=False, "
+            "fields=(text;email;value;single;multi)> don't match."
         )
         with self.assertRaisesMessage(AssertionError, msg):
             self.assertFormError(response, "form", "email", "Some error.")
@@ -722,8 +728,8 @@ class AssertFormErrorTests(SimpleTestCase):
         self.assertTemplateUsed(response, "Invalid POST Template")
 
         msg = (
-            "The form 'form' in context 0 does not contain the non-field "
-            "error 'Some error.' (actual errors: none)"
+            "The non-field errors of form <TestForm bound=True, valid=False, "
+            "fields=(text;email;value;single;multi)> don't match."
         )
         with self.assertRaisesMessage(AssertionError, msg):
             self.assertFormError(response, "form", None, "Some error.")
@@ -801,9 +807,8 @@ class AssertFormsetErrorTests(SimpleTestCase):
         "An assertion is raised if the field name is unknown"
         for prefix, kwargs in self.msg_prefixes:
             msg = (
-                prefix
-                + "The formset 'my_formset', form 0 in context 0 does not contain the "
-                "field 'Some_field'"
+                f"{prefix}The form 0 of formset <TestFormFormSet: bound=True "
+                f"valid=False total_forms=2> does not contain the field 'Some_field'."
             )
             with self.assertRaisesMessage(AssertionError, msg):
                 self.assertFormsetError(
@@ -819,9 +824,8 @@ class AssertFormsetErrorTests(SimpleTestCase):
         "An assertion is raised if the field doesn't have any errors"
         for prefix, kwargs in self.msg_prefixes:
             msg = (
-                prefix
-                + "The field 'value' on formset 'my_formset', form 1 in context 0 "
-                "contains no errors"
+                f"{prefix}The errors of field 'value' on form 1 of formset "
+                f"<TestFormFormSet: bound=True valid=False total_forms=2> don't match."
             )
             with self.assertRaisesMessage(AssertionError, msg):
                 self.assertFormsetError(
@@ -836,10 +840,9 @@ class AssertFormsetErrorTests(SimpleTestCase):
     def test_unknown_error(self):
         "An assertion is raised if the field doesn't contain the specified error"
         for prefix, kwargs in self.msg_prefixes:
-            msg = prefix + (
-                "The field 'email' on formset 'my_formset', form 0 "
-                "in context 0 does not contain the error 'Some error.' "
-                "(actual errors: ['Enter a valid email address.'])"
+            msg = (
+                f"{prefix}The errors of field 'email' on form 0 of formset "
+                f"<TestFormFormSet: bound=True valid=False total_forms=2> don't match."
             )
             with self.assertRaisesMessage(AssertionError, msg):
                 self.assertFormsetError(
@@ -866,9 +869,8 @@ class AssertFormsetErrorTests(SimpleTestCase):
         """
         for prefix, kwargs in self.msg_prefixes:
             msg = (
-                prefix
-                + "The formset 'my_formset', form 1 in context 0 does not contain any "
-                "non-field errors."
+                f"{prefix}The non-field errors of form 1 of formset <TestFormFormSet: "
+                f"bound=True valid=False total_forms=2> don't match."
             )
             with self.assertRaisesMessage(AssertionError, msg):
                 self.assertFormsetError(
@@ -886,10 +888,9 @@ class AssertFormsetErrorTests(SimpleTestCase):
         the provided error.
         """
         for prefix, kwargs in self.msg_prefixes:
-            msg = prefix + (
-                "The formset 'my_formset', form 0 in context 0 does not "
-                "contain the non-field error 'Some error.' (actual errors: "
-                "['Non-field error.'])"
+            msg = (
+                f"{prefix}The non-field errors of form 0 of formset <TestFormFormSet: "
+                f"bound=True valid=False total_forms=2> don't match."
             )
             with self.assertRaisesMessage(AssertionError, msg):
                 self.assertFormsetError(
@@ -923,9 +924,8 @@ class AssertFormsetErrorTests(SimpleTestCase):
         """
         for prefix, kwargs in self.msg_prefixes:
             msg = (
-                prefix
-                + "The formset 'my_formset' in context 0 does not contain any non-form "
-                "errors."
+                f"{prefix}The non-form errors of formset <TestFormFormSet: bound=True "
+                f"valid=False total_forms=2> don't match"
             )
             with self.assertRaisesMessage(AssertionError, msg):
                 self.assertFormsetError(
@@ -943,10 +943,9 @@ class AssertFormsetErrorTests(SimpleTestCase):
         the provided error.
         """
         for prefix, kwargs in self.msg_prefixes:
-            msg = prefix + (
-                "The formset 'my_formset' in context 0 does not contain the "
-                "non-form error 'Some error.' (actual errors: ['Forms in a set "
-                "must have distinct email addresses.'])"
+            msg = (
+                f"{prefix}The non-form errors of formset <TestFormFormSet: bound=True "
+                f"valid=False total_forms=2> don't match"
             )
             with self.assertRaisesMessage(AssertionError, msg):
                 self.assertFormsetError(
diff --git a/tests/test_utils/tests.py b/tests/test_utils/tests.py
index 038e79732b..506773b712 100644
--- a/tests/test_utils/tests.py
+++ b/tests/test_utils/tests.py
@@ -1404,46 +1404,33 @@ class AssertFormErrorTests(SimpleTestCase):
             self.assertFormError(response, "form", "field", "invalid value")
 
     def test_field_not_in_form(self):
-        msg = "The form 'form' in context 0 does not contain the field 'other_field'"
+        msg = (
+            "The form <TestForm bound=True, valid=False, fields=(field)> does not "
+            "contain the field 'other_field'."
+        )
         response = mock.Mock(context=[{"form": TestForm.invalid()}])
         with self.assertRaisesMessage(AssertionError, msg):
             self.assertFormError(response, "form", "other_field", "invalid value")
 
-    def test_field_not_in_form_multicontext(self):
-        msg = "The form 'form' in context 1 does not contain the field 'other_field'"
-        response = mock.Mock(context=[{}, {"form": TestForm.invalid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
-            self.assertFormError(response, "form", "other_field", "invalid value")
-
     def test_field_with_no_errors(self):
-        msg = "The field 'field' on form 'form' in context 0 contains no errors"
+        msg = (
+            "The errors of field 'field' on form <TestForm bound=True, valid=True, "
+            "fields=(field)> don't match."
+        )
         response = mock.Mock(context=[{"form": TestForm.valid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
-            self.assertFormError(response, "form", "field", "invalid value")
-
-    def test_field_with_no_errors_multicontext(self):
-        msg = "The field 'field' on form 'form' in context 1 contains no errors"
-        response = mock.Mock(context=[{}, {"form": TestForm.valid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
+        with self.assertRaisesMessage(AssertionError, msg) as ctx:
             self.assertFormError(response, "form", "field", "invalid value")
+        self.assertIn("[] != ['invalid value']", str(ctx.exception))
 
     def test_field_with_different_error(self):
         msg = (
-            "The field 'field' on form 'form' in context 0 does not contain "
-            "the error 'other error' (actual errors: ['invalid value'])"
+            "The errors of field 'field' on form <TestForm bound=True, valid=False, "
+            "fields=(field)> don't match."
         )
         response = mock.Mock(context=[{"form": TestForm.invalid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
-            self.assertFormError(response, "form", "field", "other error")
-
-    def test_field_with_different_error_multicontext(self):
-        msg = (
-            "The field 'field' on form 'form' in context 1 does not contain "
-            "the error 'other error' (actual errors: ['invalid value'])"
-        )
-        response = mock.Mock(context=[{}, {"form": TestForm.invalid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
+        with self.assertRaisesMessage(AssertionError, msg) as ctx:
             self.assertFormError(response, "form", "field", "other error")
+        self.assertIn("['invalid value'] != ['other error']", str(ctx.exception))
 
     def test_basic_positive_assertion(self):
         response = mock.Mock(context=[{"form": TestForm.invalid()}])
@@ -1467,8 +1454,14 @@ class AssertFormErrorTests(SimpleTestCase):
         self.assertFormError(response, "form", "field", [])
 
     def test_empty_errors_invalid_form(self):
+        msg = (
+            "The errors of field 'field' on form <TestForm bound=True, valid=False, "
+            "fields=(field)> don't match."
+        )
         response = mock.Mock(context=[{"form": TestForm.invalid()}])
-        self.assertFormError(response, "form", "field", [])
+        with self.assertRaisesMessage(AssertionError, msg) as ctx:
+            self.assertFormError(response, "form", "field", [])
+        self.assertIn("['invalid value'] != []", str(ctx.exception))
 
     def test_non_field_errors(self):
         response = mock.Mock(context=[{"form": TestForm.invalid(nonfield=True)}])
@@ -1476,17 +1469,22 @@ class AssertFormErrorTests(SimpleTestCase):
 
     @ignore_warnings(category=RemovedInDjango50Warning)
     def test_errors_none(self):
+        msg = (
+            "The errors of field 'field' on form <TestForm bound=True, valid=False, "
+            "fields=(field)> don't match."
+        )
         response = mock.Mock(context=[{"form": TestForm.invalid()}])
-        self.assertFormError(response, "form", "field", None)
+        with self.assertRaisesMessage(AssertionError, msg):
+            self.assertFormError(response, "form", "field", None)
 
     def test_errors_none_warning(self):
-        response = mock.Mock(context=[{"form": TestForm.invalid()}])
+        response = mock.Mock(context=[{"form": TestForm.valid()}])
         msg = (
             "Passing errors=None to assertFormError() is deprecated, use "
             "errors=[] instead."
         )
         with self.assertWarnsMessage(RemovedInDjango50Warning, msg):
-            self.assertFormError(response, "form", "value", None)
+            self.assertFormError(response, "form", "field", None)
 
 
 class AssertFormsetErrorTests(SimpleTestCase):
@@ -1520,8 +1518,8 @@ class AssertFormsetErrorTests(SimpleTestCase):
 
     def test_field_not_in_form(self):
         msg = (
-            "The formset 'formset', form 0 in context 0 does not contain the "
-            "field 'other_field'"
+            "The form 0 of formset <TestFormset: bound=True valid=False total_forms=1> "
+            "does not contain the field 'other_field'."
         )
         response = mock.Mock(context=[{"formset": TestFormset.invalid()}])
         with self.assertRaisesMessage(AssertionError, msg):
@@ -1533,58 +1531,25 @@ class AssertFormsetErrorTests(SimpleTestCase):
                 "invalid value",
             )
 
-    def test_field_not_in_form_multicontext(self):
-        msg = (
-            "The formset 'formset', form 0 in context 1 does not contain the "
-            "field 'other_field'"
-        )
-        response = mock.Mock(context=[{}, {"formset": TestFormset.invalid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
-            self.assertFormsetError(
-                response,
-                "formset",
-                0,
-                "other_field",
-                "invalid value",
-            )
-
     def test_field_with_no_errors(self):
         msg = (
-            "The field 'field' on formset 'formset', form 0 in context 0 "
-            "contains no errors"
+            "The errors of field 'field' on form 0 of formset <TestFormset: bound=True "
+            "valid=True total_forms=1> don't match."
         )
         response = mock.Mock(context=[{"formset": TestFormset.valid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
-            self.assertFormsetError(response, "formset", 0, "field", "invalid value")
-
-    def test_field_with_no_errors_multicontext(self):
-        msg = (
-            "The field 'field' on formset 'formset', form 0 in context 1 "
-            "contains no errors"
-        )
-        response = mock.Mock(context=[{}, {"formset": TestFormset.valid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
+        with self.assertRaisesMessage(AssertionError, msg) as ctx:
             self.assertFormsetError(response, "formset", 0, "field", "invalid value")
+        self.assertIn("[] != ['invalid value']", str(ctx.exception))
 
     def test_field_with_different_error(self):
         msg = (
-            "The field 'field' on formset 'formset', form 0 in context 0 does"
-            " not contain the error 'other error' (actual errors: ['invalid "
-            "value'])"
+            "The errors of field 'field' on form 0 of formset <TestFormset: bound=True "
+            "valid=False total_forms=1> don't match."
         )
         response = mock.Mock(context=[{"formset": TestFormset.invalid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
-            self.assertFormsetError(response, "formset", 0, "field", "other error")
-
-    def test_field_with_different_error_multicontext(self):
-        msg = (
-            "The field 'field' on formset 'formset', form 0 in context 1 does"
-            " not contain the error 'other error' (actual errors: ['invalid "
-            "value'])"
-        )
-        response = mock.Mock(context=[{}, {"formset": TestFormset.invalid()}])
-        with self.assertRaisesMessage(AssertionError, msg):
+        with self.assertRaisesMessage(AssertionError, msg) as ctx:
             self.assertFormsetError(response, "formset", 0, "field", "other error")
+        self.assertIn("['invalid value'] != ['other error']", str(ctx.exception))
 
     def test_basic_positive_assertion(self):
         response = mock.Mock(context=[{"formset": TestFormset.invalid()}])
@@ -1608,8 +1573,14 @@ class AssertFormsetErrorTests(SimpleTestCase):
         self.assertFormsetError(response, "formset", 0, "field", [])
 
     def test_empty_errors_invalid_formset(self):
+        msg = (
+            "The errors of field 'field' on form 0 of formset <TestFormset: bound=True "
+            "valid=False total_forms=1> don't match."
+        )
         response = mock.Mock(context=[{}, {"formset": TestFormset.invalid()}])
-        self.assertFormsetError(response, "formset", 0, "field", [])
+        with self.assertRaisesMessage(AssertionError, msg) as ctx:
+            self.assertFormsetError(response, "formset", 0, "field", [])
+        self.assertIn("['invalid value'] != []", str(ctx.exception))
 
     def test_non_field_errors(self):
         response = mock.Mock(
@@ -1670,11 +1641,16 @@ class AssertFormsetErrorTests(SimpleTestCase):
 
     @ignore_warnings(category=RemovedInDjango50Warning)
     def test_errors_none(self):
+        msg = (
+            "The errors of field 'field' on form 0 of formset <TestFormset: bound=True "
+            "valid=False total_forms=1> don't match."
+        )
         response = mock.Mock(context=[{"formset": TestFormset.invalid()}])
-        self.assertFormsetError(response, "formset", 0, "field", None)
+        with self.assertRaisesMessage(AssertionError, msg):
+            self.assertFormsetError(response, "formset", 0, "field", None)
 
     def test_errors_none_warning(self):
-        response = mock.Mock(context=[{"formset": TestFormset.invalid()}])
+        response = mock.Mock(context=[{"formset": TestFormset.valid()}])
         msg = (
             "Passing errors=None to assertFormsetError() is deprecated, use "
             "errors=[] instead."