test: better checking for CoverageWarnings

On Python 3.10, we were getting other warnings mixed into the warnings the tests
were looking for.  This change lets us only look at the CoverageWarnings.

2 files changed, 3 insertions, 3 deletions

diff --git a/tests/conftest.py b/tests/conftest.py
index c84f446a..4ae11542 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -27,7 +27,7 @@ pytest.register_assert_rewrite("tests.helpers")
 
 @pytest.fixture(autouse=True)
 def set_warnings():
-    """Enable DeprecationWarnings during all tests."""
+    """Configure warnings to show while running tests."""
     warnings.simplefilter("default")
     warnings.simplefilter("once", DeprecationWarning)
 
diff --git a/tests/helpers.py b/tests/helpers.py
index 40b0f481..3b0e1283 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -265,11 +265,11 @@ def assert_count_equal(a, b):
 
 def assert_coverage_warnings(warns, *msgs):
     """
-    Assert that `warns` are all CoverageWarning's, and have `msgs` as messages.
+    Assert that the CoverageWarning's in `warns` have `msgs` as messages.
     """
     assert msgs     # don't call this without some messages.
+    warns = [w for w in warns if issubclass(w.category, CoverageWarning)]
     assert len(warns) == len(msgs)
-    assert all(w.category == CoverageWarning for w in warns)
     for actual, expected in zip((w.message.args[0] for w in warns), msgs):
         if hasattr(expected, "search"):
             assert expected.search(actual), f"{actual!r} didn't match {expected!r}"