Use function to test exception when there is no element

tests/test_parser.py

@@ -30,37 +30,35 @@ def setUp(self):
         }
         self.mock_json_load = patch('parse.open_json_file')
 
-    def test_user_credentials_object_is_the_same_like_in_file(self):
+    def delete_cred_element_and_run_get_user_credentials(self, element):
+        del self.creds[element]
+        self.mock_json_load.return_value = self.creds
+        with self.assertRaises(Exception) as ue:
+            get_user_credentials()
+        return str(ue)
+
+    def test_user_credentials_object_is_same_like_in_file(self):
         self.mock_json_load.return_value = self.creds
         actual = get_user_credentials()
         self.assertEqual(actual, self.creds)
 
     def test_user_credentials_fails_if_there_is_no_user(self):
-        del self.creds['username']
-        self.mock_json_load.return_value = self.creds
-        with self.assertRaises(Exception) as ue:
-            get_user_credentials()
+        element = 'username'
         self.assertEqual(
-            'Credentials are in the wrong format (username is missing)',
-            str(ue.exception))
+            f'Credentials are in the wrong format ({element} is missing)',
+            self.test_user_credentials_object_is_same_like_in_file(element))
 
     def test_user_credentials_fails_if_there_is_no_language(self):
-        del self.creds['language']
-        self.mock_json_load.return_value = self.creds
-        with self.assertRaises(Exception) as ue:
-            get_user_credentials()
+        element = 'language'
         self.assertEqual(
-            'Credentials are in the wrong format (language is missing)',
-            str(ue.exception))
+            f'Credentials are in the wrong format ({element} is missing)',
+            self.test_user_credentials_object_is_same_like_in_file(element))
 
     def test_user_credentials_fails_if_there_is_no_password(self):
-        del self.creds['password']
-        self.mock_json_load.return_value = self.creds
-        with self.assertRaises(Exception) as ue:
-            get_user_credentials()
+        element = 'password'
         self.assertEqual(
-            'Credentials are in the wrong format (password is missing)',
-            str(ue.exception))
+            f'Credentials are in the wrong format ({element} is missing)',
+            self.test_user_credentials_object_is_same_like_in_file(element))
 
     @patch('builtins.open')
     @patch('json.load')