Update test_black-before.py

test_black-before.py

@@ -20,15 +20,21 @@ THIS_DIR = THIS_FILE.parent
 class BlackTestCase(unittest.TestCase):
     maxDiff = None
 
-    def assertFormatEqual(self, expected: str, actual: str) -> None:
-        bdv: black.DebugVisitor[Any]
-        black.out('Expected tree:', fg='green')
-        try:
-            exp_node = black.lib2to3_parse(expected)
-            bdv = black.DebugVisitor()
-            list(bdv.visit(exp_node))
-        except Exception as ve:
-            black.err(str(ve))
+    def assertFormatEqual(self, expected: str,
+                          actual: str) -> None:
+        bdv: black.DebugVisitor[self]
+        black.out('Expected tree:', fg='blue')
+        if expected:
+            try:
+                exp_node = black.lib2to3_parse(expected)
+                bdv = black.DebugVisitor()
+                list(bdv.visit(exp_node))
+            except Exception as ve:
+                black.err(str(ve))
+        else:
+            fs = partial(black.format_str, line_length=ll)
+            THIS_FILE = Path(__file__)
+            THIS_DIR = THIS_FILE.parent
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_self(self) -> None:
@@ -225,4 +231,4 @@ def test_report(self) -> None:
 
 
 if __name__ == '__main__':
-    unittest.main()
+    unittest.main()