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
37076	assertWarnsMessage() only checks the first warning for a matching message	Mike Edmunds		"`assertWarnsMessage(category, message)` fails if the ''first'' warning issued in `category` does not contain `message`, even if some later warning does match.

As a result, test cases depend on the specific order warnings are issued. This can become confusing when there are several related deprecations going in at once, or when a feature being tested uses some other feature that also issues a warning.

For example, you might expect this test to pass, but it fails with `AssertionError: 'Deprecated in MyApp' not found in 'Deprecated in Django'`:

{{{#!python
class MyAppTests(SimpleTestCase):
    def test_deprecated_in_my_app(self):
        with self.assertWarnsMessage(DeprecationWarning, ""Deprecated in MyApp""):
            # MyApp calls something in Django that happens to be deprecated:
            warnings.warn(""Deprecated in Django"", RemovedInNextVersionWarning)
            # Then MyApp issues the warning being tested:
            warnings.warn(""Deprecated in MyApp"", DeprecationWarning)
}}}

If you switch the order of the two warnings, the test passes. (And the second warning is then ignored—see #37072.)

There is a workaround by combining a very carefully crafted `ignore_warnings()` context with `assertWarnsMessage()`. (It requires knowing that the semi-documented `ignore_warnings()` also accepts a `message` argument. And that it interprets it quite differently from `assertWarnsMessage()`.)
"	Bug	new	Testing framework	6.0	Normal				Unreviewed	0	0	0	0	0	0