new test method in ItemValidationTest(); does not currently pass

src/functional_tests/test_list_item_validation.py

@@ -36,3 +36,19 @@ class ItemValidationTest(FunctionalTest):
         )
         self.get_item_input_box().send_keys(Keys.ENTER)
         self.wait_for_row_in_list_table("2. Make tea")
+
+    def test_cannot_add_duplicate_items(self):
+        self.browser.get(self.live_server_url)
+        self.get_item_input_box().send_keys("Witness divinity")
+        self.get_item_input_box().send_keys(Keys.ENTER)
+        self.wait_for_row_in_list_table("1. Witness divinity")
+
+        self.get_item_input_box().send_keys("Witness divinity")
+        self.get_item_input_box().send_keys(Keys.ENTER)
+
+        self.wait_for(
+            lambda: self.assertEqual(
+                self.browser.find_element(By.CSS_SELECTOR, ".invalid-feedback").text,
+                "You've already logged this to your list",
+            )
+        )