diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bd27136..a6e352a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -44,9 +44,8 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install responses
-          pip install coverage          
-          python ${{ github.workspace }}/setup.py install
+          pip install responses coverage
+          pip install .
       - name: Run Tests
         run: |
           python -m coverage run -m unittest
diff --git a/tests/test_client_utility_negative.py b/tests/test_client_utility_negative.py
new file mode 100644
index 0000000..13f69e0
--- /dev/null
+++ b/tests/test_client_utility_negative.py
@@ -0,0 +1,92 @@
+import hmac
+import hashlib
+import unittest
+
+from .helpers import ClientTestCase
+from razorpay.errors import SignatureVerificationError
+
+
+class TestClientValidatorNegative(ClientTestCase):
+
+    def setUp(self):
+        super(TestClientValidatorNegative, self).setUp()
+        self.webhook_payload = '{"event":"payment.authorized"}'
+        self.webhook_secret = 'test_webhook_secret'
+
+    def compute_signature(self, payload, secret):
+        return hmac.new(
+            secret.encode('utf-8'),
+            payload.encode('utf-8'),
+            hashlib.sha256
+        ).hexdigest()
+
+    def test_empty_signature_rejected(self):
+        self.assertRaises(
+            SignatureVerificationError,
+            self.client.utility.verify_webhook_signature,
+            self.webhook_payload,
+            '',
+            self.webhook_secret
+        )
+
+    def test_wrong_length_signature_rejected(self):
+        self.assertRaises(
+            SignatureVerificationError,
+            self.client.utility.verify_webhook_signature,
+            self.webhook_payload,
+            'abc123',
+            self.webhook_secret
+        )
+
+    def test_non_hex_signature_rejected(self):
+        non_hex_sig = 'z' * 64
+        self.assertRaises(
+            SignatureVerificationError,
+            self.client.utility.verify_webhook_signature,
+            self.webhook_payload,
+            non_hex_sig,
+            self.webhook_secret
+        )
+
+    def test_tampered_valid_hex_signature_rejected(self):
+        tampered_sig = 'a' * 64
+        self.assertRaises(
+            SignatureVerificationError,
+            self.client.utility.verify_webhook_signature,
+            self.webhook_payload,
+            tampered_sig,
+            self.webhook_secret
+        )
+
+    def test_valid_dynamic_signature_accepted(self):
+        valid_sig = self.compute_signature(self.webhook_payload, self.webhook_secret)
+        result = self.client.utility.verify_webhook_signature(
+            self.webhook_payload,
+            valid_sig,
+            self.webhook_secret
+        )
+        self.assertTrue(result)
+
+    def test_special_chars_in_payload(self):
+        special_payload = '{"event":"payment","data":{"notes":"Test & <script>alert(1)</script>"}}'
+        valid_sig = self.compute_signature(special_payload, self.webhook_secret)
+        result = self.client.utility.verify_webhook_signature(
+            special_payload,
+            valid_sig,
+            self.webhook_secret
+        )
+        self.assertTrue(result)
+
+    def test_unicode_in_payload(self):
+        unicode_payload = '{"event":"payment","data":{"name":"日本語テスト"}}'
+        valid_sig = self.compute_signature(unicode_payload, self.webhook_secret)
+        result = self.client.utility.verify_webhook_signature(
+            unicode_payload,
+            valid_sig,
+            self.webhook_secret
+        )
+        self.assertTrue(result)
+
+
+if __name__ == '__main__':
+    unittest.main()