fix invalid_url, add misdated_url tests

tutorials/09-readable-urls.rst

@@ -163,18 +163,22 @@ Another Test
 
 What would happen if we changed the slug or an invalid date was given in the URL?  This shouldn't matter because we only check for the model ``id``.
 
-Let's write a test for this case to make sure the correct page is displayed in this case. Our test should look like this:
+Let's write a couple more tests for this case to make sure the correct page is displayed in this case, and for when the id does not exist. Our tests should look like this:
 
 .. code-block:: python
 
-    def test_invalid_url(self):
-        entry = Entry.objects.create(title="title", body="body",
-                                     author=self.user)
-        response = self.client.get("/0000/00/00/{0}-invalid/".format(entry.id))
+    def test_misdated_url(self):
+        entry = Entry.objects.create(title="title", body="body", author=self.user)
+        response = self.client.get("/0000/00/00/{0}-misdated/".format(entry.id))
         self.assertEqual(response.status_code, 200)
         self.assertTemplateUsed(response,
                                 template_name='blog/entry_detail.html')
 
+    def test_invalid_url(self):
+        entry = Entry.objects.create(title="title", body="body", author=self.user)
+        response = self.client.get("/0000/00/00/0-invalid/")
+        self.assertEqual(response.status_code, 404)
+
 Now let's run our tests and make sure they still pass.