not getting the same precise error message, but perhaps the intent is the same?; anyway, updated views & some FTs, base.html for more dynamic error handling (tho incomplete)

src/apps/dashboard/tests/test_models.py

@@ -1,3 +1,5 @@
+from django.core.exceptions import ValidationError
+from django.db.utils import IntegrityError
 from django.test import TestCase
 from ..models import Item, List
 
@@ -28,4 +30,15 @@ class ListAndItemModelsTest(TestCase):
         self.assertEqual(first_saved_item.list, mylist)
         self.assertEqual(second_saved_item.text, "A sequel somehow better than the first")
         self.assertEqual(second_saved_item.list, mylist)
-        
+
+    def test_cannot_save_null_list_items(self):
+        mylist = List.objects.create()
+        item = Item(list=mylist, text=None)
+        with self.assertRaises(IntegrityError):
+            item.save()
+
+    def test_cannot_save_empty_list_items(self):
+        mylist = List.objects.create()
+        item = Item(list=mylist, text="")
+        with self.assertRaises(ValidationError):
+            item.full_clean()

src/apps/dashboard/tests/test_views.py

@@ -1,4 +1,5 @@
 from django.test import TestCase
+from django.utils import html
 from ..models import Item, List
 import lxml.html
 
@@ -56,6 +57,18 @@ class NewListTest(TestCase):
         new_list = List.objects.get()
         self.assertRedirects(response, f'/apps/dashboard/{new_list.id}/')
 
+    def test_validation_errors_are_sent_back_to_home_page_template(self):
+        response = self.client.post("/apps/dashboard/newlist", data={"item_text": ""})
+        self.assertEqual(response.status_code, 200)
+        self.assertTemplateUsed(response, "apps/dashboard/home.html")
+        expected_error = html.escape("You can't have an empty list item")
+        self.assertContains(response, expected_error)
+        
+    def test_invalid_list_items_never_save(self):
+        self.client.post("/apps/dashboard/newlist", data={"item_text": ""})
+        self.assertEqual(List.objects.count(), 0)
+        self.assertEqual(Item.objects.count(), 0)
+
 class NewItemTest(TestCase):
     def test_can_save_a_POST_request_to_an_existing_list(self):
         other_list = List.objects.create()

src/apps/dashboard/views.py

@@ -1,18 +1,26 @@
+from django.core.exceptions import ValidationError
 from django.shortcuts import redirect, render
 from .models import Item, List
 
 def home_page(request):
     return render(request, 'apps/dashboard/home.html')
 
+def new_list(request):
+    nulist = List.objects.create()
+    item = Item(text=request.POST['item_text'], list=nulist)
+    try:
+        item.full_clean()
+        item.save()
+    except ValidationError:
+        nulist.delete()
+        error = "You can't have an empty list item"
+        return render(request, "apps/dashboard/home.html", {"error": error})
+    return redirect(f'/apps/dashboard/{nulist.id}/')
+
 def view_list(request, list_id):
     our_list = List.objects.get(id=list_id)
     return render(request, 'apps/dashboard/list.html', {'list': our_list})
 
-def new_list(request):
-    nulist = List.objects.create()
-    Item.objects.create(text=request.POST['item_text'], list=nulist)
-    return redirect(f'/apps/dashboard/{nulist.id}/')
-
 def add_item(request, list_id):
     our_list = List.objects.get(id=list_id)
     Item.objects.create(text=request.POST['item_text'], list=our_list)

src/functional_tests/base.py

@@ -18,6 +18,16 @@ class FunctionalTest(StaticLiveServerTestCase):
     def tearDown(self):
         self.browser.quit()
 
+    def wait_for(self, fn):
+        start_time = time.time()
+        while True:
+            try:
+                return fn()
+            except (AssertionError, WebDriverException):
+                if time.time() - start_time > MAX_WAIT:
+                    raise
+                time.sleep(0.5)
+
     def wait_for_row_in_list_table(self, row_text):
         start_time = time.time()
         while True:
@@ -30,13 +40,3 @@ class FunctionalTest(StaticLiveServerTestCase):
                 if time.time() - start_time > MAX_WAIT:
                     raise
                 time.sleep(0.5)
-                
-    def wait_for(self, fn):
-        start_time = time.time()
-        while True:
-            try:
-                return fn()
-            except (AssertionError, WebDriverException):
-                if time.time() - start_time > MAX_WAIT:
-                    raise
-                time.sleep(0.5)

src/functional_tests/test_list_item_validation.py

@@ -31,5 +31,3 @@ class ItemValidationTest(FunctionalTest):
         self.browser.find_element(By.ID, 'id-new-item').send_keys("Make tea")
         self.browser.find_element(By.ID, "id-new-item").send_keys(Keys.ENTER)
         self.wait_for_row_in_list_table("2. Make tea")
-
-        self.fail("finish the fight!")

src/templates/core/base.html

@@ -14,16 +14,20 @@
         <div class="container">
             <div class="row justify-content-center p-5 bg-body-tertiary rounded-3">
                 <div class="col-lg-6 text-center">
-                    <h1 class="display-1 mb-4">Dashboard | {% block header_text %}{% endblock header_text %}</h1>
+                    <h1 class="display-1 mb-4">Dashboard</h1>
+                    <h2 class="display-2 mb-2">{% block header_text %}{% endblock header_text %}</h2>
 
                     <form method="POST" action="{% block form_action %}{% endblock form_action %}">
                         <input
                             name="item_text"
                             id="id-new-item"
-                            class="form-control form-control-lg"
+                            class="form-control form-control-lg {% if error %}is-valid{% endif %}"
                             placeholder="Enter a to-do item"
                         />
                         {% csrf_token %}
+                        {% if error %}
+                            <div class="invalid-feedback">{{ error }}</div>
+                        {% endif %}
                     </form>
                 </div>
             </div>