chore: blacken (#772)

diff --git a/tests/test__helpers.py b/tests/test__helpers.py
index e33ea71..90c75ef 100644
--- a/tests/test__helpers.py
+++ b/tests/test__helpers.py
@@ -25,10 +25,8 @@
 
 
 class PositionalTests(unittest.TestCase):
-
     def test_usage(self):
-        _helpers.positional_parameters_enforcement = (
-            _helpers.POSITIONAL_EXCEPTION)
+        _helpers.positional_parameters_enforcement = _helpers.POSITIONAL_EXCEPTION
 
         # 1 positional arg, 1 keyword-only arg.
         @_helpers.positional(1)
@@ -60,10 +58,9 @@
         with self.assertRaises(TypeError):
             function3(1, 2)
 
-    @mock.patch('googleapiclient._helpers.logger')
+    @mock.patch("googleapiclient._helpers.logger")
     def test_enforcement_warning(self, mock_logger):
-        _helpers.positional_parameters_enforcement = (
-            _helpers.POSITIONAL_WARNING)
+        _helpers.positional_parameters_enforcement = _helpers.POSITIONAL_WARNING
 
         @_helpers.positional(1)
         def function(pos, kwonly=None):
@@ -72,7 +69,7 @@
         self.assertTrue(function(1, 2))
         self.assertTrue(mock_logger.warning.called)
 
-    @mock.patch('googleapiclient._helpers.logger')
+    @mock.patch("googleapiclient._helpers.logger")
     def test_enforcement_ignore(self, mock_logger):
         _helpers.positional_parameters_enforcement = _helpers.POSITIONAL_IGNORE
 
@@ -85,24 +82,22 @@
 
 
 class AddQueryParameterTests(unittest.TestCase):
-
     def test__add_query_parameter(self):
+        self.assertEqual(_helpers._add_query_parameter("/action", "a", None), "/action")
         self.assertEqual(
-            _helpers._add_query_parameter('/action', 'a', None),
-            '/action')
+            _helpers._add_query_parameter("/action", "a", "b"), "/action?a=b"
+        )
         self.assertEqual(
-            _helpers._add_query_parameter('/action', 'a', 'b'),
-            '/action?a=b')
-        self.assertEqual(
-            _helpers._add_query_parameter('/action?a=b', 'a', 'c'),
-            '/action?a=c')
+            _helpers._add_query_parameter("/action?a=b", "a", "c"), "/action?a=c"
+        )
         # Order is non-deterministic.
         self.assertIn(
-            _helpers._add_query_parameter('/action?a=b', 'c', 'd'),
-            ['/action?a=b&c=d', '/action?c=d&a=b'])
+            _helpers._add_query_parameter("/action?a=b", "c", "d"),
+            ["/action?a=b&c=d", "/action?c=d&a=b"],
+        )
         self.assertEqual(
-            _helpers._add_query_parameter('/action', 'a', ' ='),
-            '/action?a=+%3D')
+            _helpers._add_query_parameter("/action", "a", " ="), "/action?a=+%3D"
+        )
 
 
 def assertUrisEqual(testcase, expected, actual):
@@ -123,39 +118,37 @@
 
 
 class Test_update_query_params(unittest.TestCase):
-
     def test_update_query_params_no_params(self):
-        uri = 'http://www.google.com'
-        updated = _helpers.update_query_params(uri, {'a': 'b'})
-        self.assertEqual(updated, uri + '?a=b')
+        uri = "http://www.google.com"
+        updated = _helpers.update_query_params(uri, {"a": "b"})
+        self.assertEqual(updated, uri + "?a=b")
 
     def test_update_query_params_existing_params(self):
-        uri = 'http://www.google.com?x=y'
-        updated = _helpers.update_query_params(uri, {'a': 'b', 'c': 'd&'})
-        hardcoded_update = uri + '&a=b&c=d%26'
+        uri = "http://www.google.com?x=y"
+        updated = _helpers.update_query_params(uri, {"a": "b", "c": "d&"})
+        hardcoded_update = uri + "&a=b&c=d%26"
         assertUrisEqual(self, updated, hardcoded_update)
 
     def test_update_query_params_replace_param(self):
-        base_uri = 'http://www.google.com'
-        uri = base_uri + '?x=a'
-        updated = _helpers.update_query_params(uri, {'x': 'b', 'y': 'c'})
-        hardcoded_update = base_uri + '?x=b&y=c'
+        base_uri = "http://www.google.com"
+        uri = base_uri + "?x=a"
+        updated = _helpers.update_query_params(uri, {"x": "b", "y": "c"})
+        hardcoded_update = base_uri + "?x=b&y=c"
         assertUrisEqual(self, updated, hardcoded_update)
 
     def test_update_query_params_repeated_params(self):
-        uri = 'http://www.google.com?x=a&x=b'
+        uri = "http://www.google.com?x=a&x=b"
         with self.assertRaises(ValueError):
-            _helpers.update_query_params(uri, {'a': 'c'})
+            _helpers.update_query_params(uri, {"a": "c"})
 
 
 class Test_parse_unique_urlencoded(unittest.TestCase):
-
     def test_without_repeats(self):
-        content = 'a=b&c=d'
+        content = "a=b&c=d"
         result = _helpers.parse_unique_urlencoded(content)
-        self.assertEqual(result, {'a': 'b', 'c': 'd'})
+        self.assertEqual(result, {"a": "b", "c": "d"})
 
     def test_with_repeats(self):
-        content = 'a=b&a=d'
+        content = "a=b&a=d"
         with self.assertRaises(ValueError):
             _helpers.parse_unique_urlencoded(content)