Fixed #27430 -- Added -b/--buffer option to DiscoverRunner.

3 files changed, 50 insertions, 3 deletions

diff --git a/tests/runtests.py b/tests/runtests.py
index 293396f96c..1282538a6d 100755
--- a/tests/runtests.py
+++ b/tests/runtests.py
@@ -281,7 +281,7 @@ class ActionSelenium(argparse.Action):
 
 def django_tests(verbosity, interactive, failfast, keepdb, reverse,
                  test_labels, debug_sql, parallel, tags, exclude_tags,
-                 test_name_patterns, start_at, start_after, pdb):
+                 test_name_patterns, start_at, start_after, pdb, buffer):
     state = setup(verbosity, test_labels, parallel, start_at, start_after)
     extra_tests = []
 
@@ -302,6 +302,7 @@ def django_tests(verbosity, interactive, failfast, keepdb, reverse,
         exclude_tags=exclude_tags,
         test_name_patterns=test_name_patterns,
         pdb=pdb,
+        buffer=buffer,
     )
     failures = test_runner.run_tests(
         test_labels or get_installed(),
@@ -497,6 +498,10 @@ if __name__ == "__main__":
         '--pdb', action='store_true',
         help='Runs the PDB debugger on error or failure.'
     )
+    parser.add_argument(
+        '-b', '--buffer', action='store_true',
+        help='Discard output of passing tests.',
+    )
     if PY37:
         parser.add_argument(
             '-k', dest='test_name_patterns', action='append',
@@ -563,7 +568,7 @@ if __name__ == "__main__":
             options.debug_sql, options.parallel, options.tags,
             options.exclude_tags,
             getattr(options, 'test_name_patterns', None),
-            options.start_at, options.start_after, options.pdb,
+            options.start_at, options.start_after, options.pdb, options.buffer,
         )
         if failures:
             sys.exit(1)
diff --git a/tests/test_runner/test_discover_runner.py b/tests/test_runner/test_discover_runner.py
index 2334fe6b7f..186dc52a44 100644
--- a/tests/test_runner/test_discover_runner.py
+++ b/tests/test_runner/test_discover_runner.py
@@ -6,7 +6,7 @@ from unittest import TestSuite, TextTestRunner, defaultTestLoader, skipUnless
 from django.db import connections
 from django.test import SimpleTestCase
 from django.test.runner import DiscoverRunner
-from django.test.utils import captured_stdout
+from django.test.utils import captured_stderr, captured_stdout
 from django.utils.version import PY37
 
 
@@ -269,6 +269,34 @@ class DiscoverRunnerTests(SimpleTestCase):
         with self.assertRaisesMessage(ValueError, msg):
             DiscoverRunner(pdb=True, parallel=2)
 
+    def test_buffer_with_parallel(self):
+        msg = (
+            'You cannot use -b/--buffer with parallel tests; pass '
+            '--parallel=1 to use it.'
+        )
+        with self.assertRaisesMessage(ValueError, msg):
+            DiscoverRunner(buffer=True, parallel=2)
+
+    def test_buffer_mode_test_pass(self):
+        runner = DiscoverRunner(buffer=True, verbose=0)
+        with captured_stdout() as stdout, captured_stderr() as stderr:
+            suite = runner.build_suite([
+                'test_runner_apps.buffer.tests_buffer.WriteToStdoutStderrTestCase.test_pass',
+            ])
+            runner.run_suite(suite)
+        self.assertNotIn('Write to stderr.', stderr.getvalue())
+        self.assertNotIn('Write to stdout.', stdout.getvalue())
+
+    def test_buffer_mode_test_fail(self):
+        runner = DiscoverRunner(buffer=True, verbose=0)
+        with captured_stdout() as stdout, captured_stderr() as stderr:
+            suite = runner.build_suite([
+                'test_runner_apps.buffer.tests_buffer.WriteToStdoutStderrTestCase.test_fail',
+            ])
+            runner.run_suite(suite)
+        self.assertIn('Write to stderr.', stderr.getvalue())
+        self.assertIn('Write to stdout.', stdout.getvalue())
+
 
 class DiscoverRunnerGetDatabasesTests(SimpleTestCase):
     runner = DiscoverRunner(verbosity=2)
diff --git a/tests/test_runner_apps/buffer/tests_buffer.py b/tests/test_runner_apps/buffer/tests_buffer.py
new file mode 100644
index 0000000000..36bc315d6d
--- /dev/null
+++ b/tests/test_runner_apps/buffer/tests_buffer.py
@@ -0,0 +1,14 @@
+import sys
+from unittest import TestCase
+
+
+class WriteToStdoutStderrTestCase(TestCase):
+    def test_pass(self):
+        sys.stderr.write('Write to stderr.')
+        sys.stdout.write('Write to stdout.')
+        self.assertTrue(True)
+
+    def test_fail(self):
+        sys.stderr.write('Write to stderr.')
+        sys.stdout.write('Write to stdout.')
+        self.assertTrue(False)