Improve type-checking in OutcomeException

Fix #5578

1 files changed, 16 insertions, 0 deletions

diff --git a/testing/test_runner.py b/testing/test_runner.py
index 15180c071..82e413518 100644
--- a/testing/test_runner.py
+++ b/testing/test_runner.py
@@ -11,6 +11,7 @@ from _pytest import main
 from _pytest import outcomes
 from _pytest import reports
 from _pytest import runner
+from _pytest.outcomes import OutcomeException
 
 
 class TestSetupState:
@@ -990,3 +991,18 @@ class TestReportContents:
         rep = reports[1]
         assert rep.capstdout == ""
         assert rep.capstderr == ""
+
+
+def test_outcome_exception_bad_msg():
+    """Check that OutcomeExceptions validate their input to prevent confusing errors (#5578)"""
+
+    def func():
+        pass
+
+    expected = (
+        "OutcomeException expected string as 'msg' parameter, got 'function' instead.\n"
+        "Perhaps you meant to use a mark?"
+    )
+    with pytest.raises(TypeError) as excinfo:
+        OutcomeException(func)
+    assert str(excinfo.value) == expected