diff --git a/tests/test_black.py b/tests/test_black.py
index 29a0731..347eaf6 100644
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -175,8 +175,9 @@ def test_piping(self) -> None:
         )
         self.assertEqual(result.exit_code, 0)
         self.assertFormatEqual(expected, result.output)
-        black.assert_equivalent(source, result.output)
-        black.assert_stable(source, result.output, DEFAULT_MODE)
+        if source != result.output:
+            black.assert_equivalent(source, result.output)
+            black.assert_stable(source, result.output, DEFAULT_MODE)
 
     def test_piping_diff(self) -> None:
         diff_header = re.compile(
@@ -1904,7 +1905,7 @@ def fail(*args: Any, **kwargs: Any) -> None:
             critical=fail,
             log=fail,
         ):
-            ff(THIS_FILE)
+            ff(THIS_DIR / "util.py")
 
     def test_invalid_config_return_code(self) -> None:
         tmp_file = Path(black.dump_to_file())
diff --git a/tests/test_format.py b/tests/test_format.py
index e59d521..5c78afe 100644
--- a/tests/test_format.py
+++ b/tests/test_format.py
@@ -7,7 +7,6 @@
 from tests.util import (
     BlackBaseTestCase,
     fs,
-    ff,
     DEFAULT_MODE,
     dump_to_stderr,
     read_data,
@@ -135,11 +134,11 @@ def test_experimental_format(self, filename: str) -> None:
     def test_source_is_formatted(self, filename: str) -> None:
         path = THIS_DIR.parent / filename
         self.check_file(str(path), DEFAULT_MODE, data=False)
-        self.assertFalse(ff(path))
 
     def check_file(self, filename: str, mode: black.Mode, *, data: bool = True) -> None:
         source, expected = read_data(filename, data=data)
         actual = fs(source, mode=mode)
         self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, mode)
+        if source != actual:
+            black.assert_equivalent(source, actual)
+            black.assert_stable(source, actual, mode)