style: fix pylint and ruff issues in LTI nonce replay test

- Add missing class docstring to TimestampAndNonceValidatorTest (C0115)
- Move time.time patch from class decorator into setUp/addCleanup to
  eliminate unused mock parameters in every test method (PT019)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: feanil

lms/djangoapps/lti_provider/tests/test_signature_validator.py

@@ -123,46 +123,51 @@ def test_verification_parameters(self, verify_mock):
             request.build_absolute_uri(), 'POST', body.encode('utf-8'), headers)
 
 
-@patch('lms.djangoapps.lti_provider.signature_validator.time.time', return_value=FIXED_TIMESTAMP)
 class TimestampAndNonceValidatorTest(CacheIsolationMixin, TestCase):
-    ENABLED_CACHES = ['default']
     """
-    Tests for validate_timestamp_and_nonce. The clock is frozen via a class-level
-    patch so every test method receives a consistent `time.time` return value.
+    Tests for the validate_timestamp_and_nonce method in SignatureValidator.
     """
 
+    ENABLED_CACHES = ['default']
+
     def setUp(self):
         super().setUp()
+        patcher = patch(
+            'lms.djangoapps.lti_provider.signature_validator.time.time',
+            return_value=FIXED_TIMESTAMP,
+        )
+        patcher.start()
+        self.addCleanup(patcher.stop)
         self.validator = SignatureValidator(get_lti_consumer())
 
     def _call(self, timestamp, nonce, client_key='Consumer Key'):
         return self.validator.validate_timestamp_and_nonce(
             client_key, str(timestamp), nonce, request=None,
         )
 
-    def test_valid_timestamp_and_new_nonce(self, _mock_time):
+    def test_valid_timestamp_and_new_nonce(self):
         assert self._call(FIXED_TIMESTAMP, 'nonce-a')
 
-    def test_stale_timestamp_rejected(self, _mock_time):
+    def test_stale_timestamp_rejected(self):
         assert not self._call(FIXED_TIMESTAMP - 301, 'nonce-b')
 
-    def test_future_timestamp_rejected(self, _mock_time):
+    def test_future_timestamp_rejected(self):
         assert not self._call(FIXED_TIMESTAMP + 301, 'nonce-c')
 
-    def test_malformed_timestamp_rejected(self, _mock_time):
+    def test_malformed_timestamp_rejected(self):
         assert not self.validator.validate_timestamp_and_nonce(
             'Consumer Key', 'not-a-number', 'nonce-d', request=None,
         )
 
-    def test_replay_rejected(self, _mock_time):
+    def test_replay_rejected(self):
         assert self._call(FIXED_TIMESTAMP, 'nonce-e')
         assert not self._call(FIXED_TIMESTAMP, 'nonce-e')
 
-    def test_different_nonce_same_consumer_accepted(self, _mock_time):
+    def test_different_nonce_same_consumer_accepted(self):
         assert self._call(FIXED_TIMESTAMP, 'nonce-f1')
         assert self._call(FIXED_TIMESTAMP, 'nonce-f2')
 
-    def test_same_nonce_different_consumer_accepted(self, _mock_time):
+    def test_same_nonce_different_consumer_accepted(self):
         # Nonces are scoped per client_key; the same nonce string from two
         # different consumers must not block each other.
         assert self._call(FIXED_TIMESTAMP, 'nonce-g', client_key='Consumer Key')