test: use mock to simulate behaviour of IBM Cloud API

Author: tmishina

test/resource/.gitignore

@@ -13,52 +13,45 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 """Arboretim IBM Cloud IAM utitity module tests."""
-import configparser
-import textwrap
 import unittest
+from unittest import mock
 
 from arboretum.common.iam_ibm import get_tokens
 
-from requests import HTTPError
+from requests import HTTPError, Response
 
 
-class IamIbmTest(unittest.TestCase):
-    """Arboretim IBM Cloud IAM functions tests."""
+def _mock_requests_post(*args, **kwargs):
+    data = kwargs['data']
+    kw = 'apikey='
+    idx = data.find(kw)
+    api_key = data[idx + len(kw):]
 
-    @classmethod
-    def setUpClass(cls):
-        """Initialize test class."""
-        creds = configparser.ConfigParser()
-        cred_filepath = 'test/resource/credentials'
-        config_files = creds.read(cred_filepath, encoding='utf-8')
-        config_example = textwrap.dedent(
-            """
-            Example credential file contents:
-            (replace "S1A2_DQp..." with valid API key string)
+    def json_function(**kwargs):
+        return {
+            'access_token': 'yI6ICJodHRwOi8vc2VydmVyLmV4YW1y'
+            'I6ICJodHRwOi8vc2VydmVyLmV4YW1',
+            'refresh_token': 'yI6ICJodHRwOi8vc2VydmVyLmV4YW1y'
+            'I6ICJodHRwOi8vc2VydmVyLmV4YW1'
+        }
 
-            [ibm_cloud]
-            test_api_key=S1A2_DQp...
-        """
-        )
-        if len(config_files) == 0:
+    resp = Response()
+    if len(api_key) > len('yI6ICJodHRwOi8vc2VydmVyLmV4YW1'):
+        resp.status_code = 200
+        resp.json = json_function
+    else:
+        raise HTTPError()  # status_code is automatically set to 400.
+    return resp
 
-            raise RuntimeError(
-                'Failed to read credential file: '
-                f'{cred_filepath}\n'
-                f'{config_example}'
-            )
-        try:
-            cls._api_key = creds['ibm_cloud']['test_api_key']
-        except KeyError:
-            raise RuntimeError(
-                'Failed to read API key from file: '
-                f'{cred_filepath}\n'
-                f'{config_example}'
-            )
 
+class IamIbmTest(unittest.TestCase):
+    """Arboretim IBM Cloud IAM functions tests."""
+
+    @mock.patch('requests.post', new=_mock_requests_post)
     def test_get_tokens_success(self):
         """Ensure that an API call with valid API key returns valid tokens."""
-        access_token, refresh_token = get_tokens(self._api_key)
+        api_key = 'yI6ICJodHRwOi8vc2VydmVyLmV4YW1xxxx'
+        access_token, refresh_token = get_tokens(api_key)
 
         # spec of access_token and refresh_token
         # https://cloud.ibm.com/docs/mobilefoundation?topic=mobilefoundation-basic_authentication
@@ -77,4 +70,7 @@ def test_get_tokens_error(self):
         fake_api_key = 'xxx'
         with self.assertRaises(HTTPError) as cm:
             access_token, refresh_token = get_tokens(fake_api_key)
-        self.assertEqual(400, cm.exception.response.status_code)
+        status_code = cm.exception.response.status_code
+        self.assertEqual(
+            400, status_code, f'status_code is {status_code}, not 400.'
+        )