diff --git a/mod_test/controllers.py b/mod_test/controllers.py
index 62844bbe..691ab698 100644
--- a/mod_test/controllers.py
+++ b/mod_test/controllers.py
@@ -416,6 +416,10 @@ def restart_test(test_id):
     :type test_id: int
     """
     test = Test.query.filter(Test.id == test_id).first()
+    if test is None:
+        g.log.error(f"test with id: {test_id} not found!")
+        raise TestNotFoundException(f"Test with id {test_id} does not exist")
+
     test_fork = TestFork.query.filter(TestFork.user_id == g.user.id, TestFork.test_id == test_id).first()
     if not g.user.is_admin and test_fork is None:
         g.log.warning(f"user with id: {g.user.id} tried to access restricted endpoint")
@@ -441,6 +445,10 @@ def stop_test(test_id):
     :type test_id: int
     """
     test = Test.query.filter(Test.id == test_id).first()
+    if test is None:
+        g.log.error(f"test with id: {test_id} not found!")
+        raise TestNotFoundException(f"Test with id {test_id} does not exist")
+
     test_fork = TestFork.query.filter(TestFork.user_id == g.user.id, TestFork.test_id == test_id).first()
     if not g.user.is_admin and test_fork is None:
         g.log.warning(f"user with id: {g.user.id} tried to access restricted endpoint")
diff --git a/tests/test_test/test_controllers.py b/tests/test_test/test_controllers.py
index 1fa043fb..eeec69b2 100644
--- a/tests/test_test/test_controllers.py
+++ b/tests/test_test/test_controllers.py
@@ -109,6 +109,50 @@ def test_stop_fails_on_no_permission(self):
             response = c.get('/test/stop_test/1')
             self.assert403(response)
 
+    def test_restart_nonexistent_test_as_admin(self):
+        """Test restart of a nonexistent test as admin returns 404."""
+        self.create_user_with_role(
+            self.user.name, self.user.email, self.user.password, Role.admin)
+        with self.app.test_client() as c:
+            c.post(
+                '/account/login', data=self.create_login_form_data(self.user.email, self.user.password))
+            response = c.get('/test/restart_test/99999')
+            self.assertEqual(response.status_code, 404)
+            self.assert_template_used('test/test_not_found.html')
+
+    def test_restart_nonexistent_test_as_tester(self):
+        """Test restart of a nonexistent test as tester returns 404."""
+        self.create_user_with_role(
+            self.user.name, self.user.email, self.user.password, Role.tester)
+        with self.app.test_client() as c:
+            c.post(
+                '/account/login', data=self.create_login_form_data(self.user.email, self.user.password))
+            response = c.get('/test/restart_test/99999')
+            self.assertEqual(response.status_code, 404)
+            self.assert_template_used('test/test_not_found.html')
+
+    def test_stop_nonexistent_test_as_admin(self):
+        """Test stop of a nonexistent test as admin returns 404."""
+        self.create_user_with_role(
+            self.user.name, self.user.email, self.user.password, Role.admin)
+        with self.app.test_client() as c:
+            c.post(
+                '/account/login', data=self.create_login_form_data(self.user.email, self.user.password))
+            response = c.get('/test/stop_test/99999')
+            self.assertEqual(response.status_code, 404)
+            self.assert_template_used('test/test_not_found.html')
+
+    def test_stop_nonexistent_test_as_tester(self):
+        """Test stop of a nonexistent test as tester returns 404."""
+        self.create_user_with_role(
+            self.user.name, self.user.email, self.user.password, Role.tester)
+        with self.app.test_client() as c:
+            c.post(
+                '/account/login', data=self.create_login_form_data(self.user.email, self.user.password))
+            response = c.get('/test/stop_test/99999')
+            self.assertEqual(response.status_code, 404)
+            self.assert_template_used('test/test_not_found.html')
+
     def test_get_json_data_throw_not_found_error(self):
         """Test if get_json_data throws Error 404."""
         response = self.app.test_client().get('/test/get_json_data/99999')