Fixed the docstring for the cube files test class.

regtests/regtests.py

@@ -1341,7 +1341,7 @@ class TestElectronicStructureMethod(unittest.TestCase):
 
 
 class TestCubeFiles(unittest.TestCase):
-    """Tests that different methods are recognized correctly.
+    """Tests that a calculation with a cube file is opened correctly.
     """
     def test_electron_density(self):
         get_result("cube/single_point_default_name")