id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
35622	Make unittest ignore Django frames in tracebacks	Adam Johnson	Adam Johnson	"Make unittest ignore Django frames in tracebacks

The module containing Django’s custom assert methods (`django.test.testcases`) does not have the `__unittest` attribute. This makes unit test unnecessarily display frames in those methods when tests fail, and opens the debugger there when using `--pdb`.

unittest ignores stack frames in modules with `__unittest` defined ([https://github.com/python/cpython/blob/bc264eac3ad14dab748e33b3d714c2674872791f/Lib/unittest/result.py#L207 source], [https://github.com/python/cpython/blob/bc264eac3ad14dab748e33b3d714c2674872791f/Lib/unittest/case.py#L19 example]). If add this in `django.test.testcases`, we get the same behaviour.

Take these two failing tests:

{{{
from django.test import SimpleTestCase


class ExampleTests(SimpleTestCase):
    def test_1_unittest_assert(self):
        x = 0
        self.assertTrue(x)

    def test_2_django_assert(self):
        y = ""[]""
        self.assertJSONEqual(""{}"", y)
}}}

Running them gives:

{{{
./manage.py test
Found 2 test(s).
System check identified no issues (0 silenced).
FF
======================================================================
FAIL: test_1_unittest_assert (example.tests.ExampleTests.test_1_unittest_assert)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/.../example/tests.py"", line 7, in test_1_unittest_assert
    self.assertTrue(x)
AssertionError: 0 is not true

======================================================================
FAIL: test_2_django_assert (example.tests.ExampleTests.test_2_django_assert)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/.../example/tests.py"", line 11, in test_2_django_assert
    self.assertJSONEqual(""{}"", y)
  File ""/.../django/test/testcases.py"", line 1020, in assertJSONEqual
    self.assertEqual(data, expected_data, msg=msg)
AssertionError: {} != []

----------------------------------------------------------------------
Ran 2 tests in 0.001s

FAILED (failures=2)
}}}

Notice how the only frame shown for `test_1_unittest_assert` is in the test itself, whilst `test_2_django_assert` contains the frame from within Django. This is useless noise for the user, which is why unittest hides its own frames

Also, when running tests with `--pdb`, pdb opens within the test for `test_1_unittest_assert`.
We can run `x` to check the value of variable `x` and `c` to continue:

{{{
$ ./manage.py test --pdb
Found 2 test(s).
System check identified no issues (0 silenced).
F
Opening PDB: AssertionError('0 is not true')
> /.../example/tests.py(7)test_1_unittest_assert()
-> self.assertTrue(x)
(Pdb) x
0
(Pdb) c
}}}

But in `test_2_django_assert`, pdb opens within the `assertJSONEqual` method.
We need to run `u` (`up`) to traverse the stack to the test method before we can do any meaningful debugging.
(Some assert methods require multiple `u` commands.)

{{{
F
Opening PDB: AssertionError('{} != []')
> /.../django/test/testcases.py(1020)assertJSONEqual()
-> self.assertEqual(data, expected_data, msg=msg)
(Pdb) u
> /.../example/tests.py(11)test_2_django_assert()
-> self.assertJSONEqual(""{}"", y)
(Pdb) y
'[]'
(Pdb) c
}}}"	Cleanup/optimization	closed	Testing framework	dev	Normal	fixed			Ready for checkin	1	0	0	0	0	0