Closes #37: Cover auth module with tests

Cover get token, refresh token processes. Cover invalid credentials or invalid data tries to get token
`view.py:authorize()` is left uncovered and revoke token is uncovered because of bug in `flask-oauthlib`

tests/modules/auth/conftest.py

@@ -0,0 +1,44 @@
+# encoding: utf-8
+import datetime
+import pytest
+
+
+@pytest.yield_fixture()
+def regular_user_oauth2_client(regular_user ,db):
+    # pylint: disable=invalid-name,unused-argument
+    from app.modules.auth.models import OAuth2Client
+
+    admin_oauth2_client_instance = OAuth2Client(
+        user=regular_user,
+        client_id='regular_user_client',
+        client_secret='regular_user_secret',
+        redirect_uris=[],
+        default_scopes=[]
+    )
+
+    db.session.add(admin_oauth2_client_instance)
+    db.session.commit()
+    yield admin_oauth2_client_instance
+    db.session.delete(admin_oauth2_client_instance)
+    db.session.commit()
+
+
+@pytest.yield_fixture()
+def regular_user_oauth2_token(regular_user_oauth2_client, db):
+    from app.modules.auth.models import OAuth2Token
+
+    regular_user_token = OAuth2Token(
+        client=regular_user_oauth2_client,
+        user=regular_user_oauth2_client.user,
+        access_token='test_token',
+        refresh_token='test_refresh_token',
+        expires=datetime.datetime.now() + datetime.timedelta(seconds=3600),
+        token_type=OAuth2Token.TokenTypes.Bearer,
+        scopes=[]
+    )
+
+    db.session.add(regular_user_token)
+    db.session.commit()
+    yield regular_user_token
+    db.session.delete(regular_user_token)
+    db.session.commit()

tests/modules/auth/resources/test_token.py

@@ -0,0 +1,144 @@
+from base64 import b64encode
+
+import pytest
+
+
+def test_regular_user_can_retrieve_token(
+        flask_app_client,
+        regular_user,
+        regular_user_oauth2_client
+    ):
+    response = flask_app_client.post(
+        '/auth/oauth2/token',
+        content_type='application/x-www-form-urlencoded',
+        data={
+            'username': regular_user.username,
+            'password': 'regular_user_password',
+            'client_id': regular_user_oauth2_client.client_id,
+            'client_secret': regular_user_oauth2_client.client_secret,
+            'grant_type': 'password',
+        },
+    )
+
+    assert response.status_code == 200
+    assert set(response.json.keys()) >= {'access_token', 'refresh_token'}
+
+
+def test_regular_user_cant_retrieve_token_without_credentials(
+        flask_app_client,
+        regular_user,
+    ):
+    response = flask_app_client.post(
+        '/auth/oauth2/token',
+        content_type='application/x-www-form-urlencoded',
+        data={
+            'username': regular_user.username,
+            'password': 'regular_user_password',
+            'grant_type': 'password',
+        },
+    )
+
+    assert response.status_code == 401
+
+
+def test_regular_user_cant_retrieve_token_with_invalid_credentials(
+        flask_app_client,
+        regular_user,
+    ):
+    response = flask_app_client.post(
+        '/auth/oauth2/token',
+        content_type='application/x-www-form-urlencoded',
+        data={
+            'username': regular_user.username,
+            'password': 'wrong_password',
+            'client_id': 'wrong_client_id',
+            'client_secret': 'wrong_client_secret',
+            'grant_type': 'password',
+        },
+    )
+
+    assert response.status_code == 401
+
+
+def test_regular_user_cant_retrieve_token_without_any_data(
+        flask_app_client,
+    ):
+    response = flask_app_client.post(
+        '/auth/oauth2/token',
+        content_type='application/x-www-form-urlencoded',
+        data={},
+    )
+
+    assert response.status_code == 400
+
+
+def test_regular_user_can_refresh_token(
+        flask_app_client,
+        regular_user_oauth2_token,
+    ):
+    refresh_token_response = flask_app_client.post(
+        '/auth/oauth2/token',
+        content_type='application/x-www-form-urlencoded',
+        data={
+            'refresh_token': regular_user_oauth2_token.refresh_token,
+            'client_id': regular_user_oauth2_token.client.client_id,
+            'client_secret': regular_user_oauth2_token.client.client_secret,
+            'grant_type': 'refresh_token',
+        },
+    )
+
+    assert refresh_token_response.status_code == 200
+    assert set(refresh_token_response.json.keys()) >= {'access_token'}
+
+
+def test_regular_user_cant_refresh_token_with_invalid_refresh_token(
+        flask_app_client,
+        regular_user_oauth2_token,
+    ):
+    refresh_token_response = flask_app_client.post(
+        '/auth/oauth2/token',
+        content_type='application/x-www-form-urlencoded',
+        data={
+            'refresh_token': 'wrong_refresh_token',
+            'client_id': regular_user_oauth2_token.client.client_id,
+            'client_secret': regular_user_oauth2_token.client.client_secret,
+            'grant_type': 'refresh_token',
+        },
+    )
+
+    assert refresh_token_response.status_code == 401
+
+
+def test_user_cant_refresh_token_without_any_data(
+        flask_app_client,
+    ):
+    refresh_token_response = flask_app_client.post(
+        '/auth/oauth2/token',
+        content_type='application/x-www-form-urlencoded',
+        data={},
+    )
+
+    assert refresh_token_response.status_code == 400
+
+
+# There is a bug in flask-oauthlib: https://github.com/lepture/flask-oauthlib/issues/233
+@pytest.mark.xfail
+def test_regular_user_can_revoke_token(
+        flask_app_client,
+        regular_user_oauth2_token,
+    ):
+    data = {
+        'token': regular_user_oauth2_token.refresh_token,
+        'client_id': regular_user_oauth2_token.client.client_id,
+        'client_secret': regular_user_oauth2_token.client.client_secret,
+    }
+    revoke_token_response = flask_app_client.post(
+        '/auth/oauth2/revoke',
+        content_type='application/x-www-form-urlencoded',
+        headers={
+            'Authorization': 'Basic %s' % b64encode(('%s:%s' % (regular_user_oauth2_token.client.client_id, regular_user_oauth2_token.client.client_secret)).encode('utf-8')),
+        },
+        data=data,
+    )
+
+    assert revoke_token_response.status_code == 200