Remove a lot of nonsense from refactoring tests

test/test_integration.py

@@ -58,5 +58,5 @@ def test_refactor(refactor_case):
 
     :type refactor_case: :class:`.refactor.RefactoringCase`
     """
-    diff = refactor_case.run()
-    assert_case_equal(refactor_case, diff, refactor_case.desired)
+    diff = refactor_case.calculate_diff()
+    assert_case_equal(refactor_case, diff, refactor_case.desired_diff)