subtests: fix inconcistent handling of non-string messages

Author: radoering

AUTHORS

@@ -384,6 +384,7 @@ Ralf Schmitt
 Ralph Giles
 Ram Rachum
 Ran Benita
+Randy Döring
 Raphael Castaneda
 Raphael Pierzina
 Rafal Semik

changelog/14195.bugfix.rst

@@ -0,0 +1 @@
+Fixed an issue where non-string messages passed to `unittest.TestCase.subTest()` are not printed.

src/_pytest/unittest.py

@@ -16,6 +16,7 @@
 from typing import Any
 from typing import TYPE_CHECKING
 from unittest import TestCase
+from unittest.case import _subtest_msg_sentinel  # type: ignore[attr-defined]
 
 import _pytest._code
 from _pytest._code import ExceptionInfo
@@ -427,7 +428,7 @@ def addSubTest(
             when="call",
             _ispytest=True,
         )
-        msg = test._message if isinstance(test._message, str) else None  # type: ignore[attr-defined]
+        msg = None if test._message is _subtest_msg_sentinel else str(test._message)  # type: ignore[attr-defined]
         report = self.ihook.pytest_runtest_makereport(item=self, call=call_info)
         sub_report = SubtestReport._new(
             report,

testing/test_subtests.py

@@ -373,6 +373,30 @@ def test_foo(subtests):
     )
 
 
+def test_msg_not_a_string(
+    pytester: pytest.Pytester, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.setenv("COLUMNS", "120")
+    pytester.makepyfile(
+        """
+        def test_int_msg(subtests):
+            with subtests.test(42):
+                assert False, "subtest failure"
+
+        def test_no_msg(subtests):
+            with subtests.test():
+                assert False, "subtest failure"
+        """
+    )
+    result = pytester.runpytest()
+    result.stdout.fnmatch_lines(
+        [
+            "SUBFAILED[[]42[]] test_msg_not_a_string.py::test_int_msg - AssertionError: subtest failure",
+            "SUBFAILED(<subtest>) test_msg_not_a_string.py::test_no_msg - AssertionError: subtest failure",
+        ]
+    )
+
+
 @pytest.mark.parametrize("flag", ["--last-failed", "--stepwise"])
 def test_subtests_last_failed_step_wise(pytester: pytest.Pytester, flag: str) -> None:
     """Check that --last-failed and --step-wise correctly rerun tests with failed subtests."""
@@ -622,6 +646,32 @@ def test_foo(self):
             "SUBSKIPPED[[]subtest 1[]] [[]1[]] *.py:*: skip subtest 1"
         )
 
+    def test_msg_not_a_string(
+        self, pytester: pytest.Pytester, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        monkeypatch.setenv("COLUMNS", "120")
+        pytester.makepyfile(
+            """
+            from unittest import TestCase
+
+            class T(TestCase):
+                def test_int_msg(self):
+                    with self.subTest(42):
+                        assert False, "subtest failure"
+
+                def test_no_msg(self):
+                    with self.subTest():
+                        assert False, "subtest failure"
+            """
+        )
+        result = pytester.runpytest()
+        result.stdout.fnmatch_lines(
+            [
+                "SUBFAILED[[]42[]] test_msg_not_a_string.py::T::test_int_msg - AssertionError: subtest failure",
+                "SUBFAILED(<subtest>) test_msg_not_a_string.py::T::test_no_msg - AssertionError: subtest failure",
+            ]
+        )
+
 
 class TestCapture:
     def create_file(self, pytester: pytest.Pytester) -> None: