Improve error messages from BlackRunner

diff --git a/tests/test_black.py b/tests/test_black.py
index 8fafabddda8cf4480958fb37c2af14360f52c59d..baa44ab32c9ce33de82a442e97a5d7f33dee27e6 100644 (file)
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -162,7 +162,12 @@ class BlackTestCase(unittest.TestCase):
         self.assertEqual(
             result.exit_code,
             exit_code,
-            msg=f"Failed with args: {args}. Stderr: {runner.stderr_bytes.decode()!r}",
+            msg=(
+                f"Failed with args: {args}\n"
+                f"stdout: {runner.stdout_bytes.decode()!r}\n"
+                f"stderr: {runner.stderr_bytes.decode()!r}\n"
+                f"exception: {result.exception}"
+            ),
         )
 
     @patch("black.dump_to_file", dump_to_stderr)