[trivial] Use proper test cases on `unittest`
diff --git a/tests/test_black.py b/tests/test_black.py
index 91d10581f6f..202fe23ddcd 100644
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -940,8 +940,8 @@ def err(msg: str, **kwargs: Any) -> None:
                 self.assertFormatEqual("j = [1, 2, 3]", "j = [1, 2, 3,]")
 
         out_str = "".join(out_lines)
-        self.assertTrue("Expected tree:" in out_str)
-        self.assertTrue("Actual tree:" in out_str)
+        self.assertIn("Expected tree:", out_str)
+        self.assertIn("Actual tree:", out_str)
         self.assertEqual("".join(err_lines), "")
 
     @event_loop()
diff --git a/tests/test_primer.py b/tests/test_primer.py
index 9bb401574ca..0a9d2aec495 100644
--- a/tests/test_primer.py
+++ b/tests/test_primer.py
@@ -181,7 +181,7 @@ def test_gen_check_output(self) -> None:
         stdout, stderr = loop.run_until_complete(
             lib._gen_check_output([lib.BLACK_BINARY, "--help"])
         )
-        self.assertTrue("The uncompromising code formatter" in stdout.decode("utf8"))
+        self.assertIn("The uncompromising code formatter", stdout.decode("utf8"))
         self.assertEqual(None, stderr)
 
         # TODO: Add a test to see failure works on Windows
