Merge pull request googleapis#105 from jgeewax/firestore-testing-change

Conform to standard testing pattern.

firestore/unit_tests/test_client.py

@@ -14,10 +14,17 @@
 
 import unittest
 
-from google.cloud.firestore import Client
-
 
 class TestFirestore(unittest.TestCase):
+
+    @staticmethod
+    def _get_target_class():
+        from google.cloud.firestore.client import Client
+        return Client
+
+    def _make_one(self, *args, **kwargs):
+        return self._get_target_class()(*args, **kwargs)
+
     def test_constructor(self):
         with self.assertRaises(NotImplementedError):
-            Client('my-project-id')
+            self._make_one('my-project-id')