def test_add_column_raises_error_if_column_is_already_defined(self):
schema = Schema()
schema.add_column('A')
with self.assertRaises(SchemaError) as ctx:
schema.add_column('A')
self.assertEqual("Column 'A' is already defined.", str(ctx.exception))
def test_add_column_does_not_add_a_column_if_it_raises_error(self):
schema = Schema()
schema.add_column('A')
with self.assertRaises(SchemaError):
schema.add_column('A')
self.assertEqual(('A', ), schema.columns)
def test_can_add_columns_to_a_schema(self):
schema = Schema()
schema.add_column('A')
schema.add_column('B')
schema.add_column('C')
self.assertEqual(('A', 'B', 'C'), schema.columns)