diff --git a/.python-version b/.python-version
new file mode 100644
index 0000000..2c07333
--- /dev/null
+++ b/.python-version
@@ -0,0 +1 @@
+3.11
diff --git a/spkrepo/tests/test_frontend.py b/spkrepo/tests/test_frontend.py
index 632161c..935811f 100644
--- a/spkrepo/tests/test_frontend.py
+++ b/spkrepo/tests/test_frontend.py
@@ -196,13 +196,23 @@ def test_post_generate_api_key_not_developer(self):
 
 
 class RegisterTestCase(BaseTestCase):
-    def test_unique_user_username(self):
+    def test_invalid_email(self):
         data = dict(
             username="test",
             email="test@test.com",
             password="password",
             password_confirm="password",
         )
+        response = self.client.post(url_for_security("register"), data=data)
+        self.assertIn("Invalid email address", response.data.decode())
+
+    def test_unique_user_username(self):
+        data = dict(
+            username="test",
+            email="test@gmail.com",
+            password="password",
+            password_confirm="password",
+        )
         self.client.post(url_for_security("register"), data=data)
         response = self.client.post(url_for_security("register"), data=data)
         self.assertIn("Username already taken", response.data.decode())