Added more tests for model field choices validation.

tests/invalid_models_tests/test_ordinary_fields.py

@@ -149,6 +149,21 @@ class CharFieldTests(TestCase):
             ),
         ])
 
+    def test_non_iterable_choices_two_letters(self):
+        """Two letters isn't a valid choice pair."""
+        class Model(models.Model):
+            field = models.CharField(max_length=10, choices=['ab'])
+
+        field = Model._meta.get_field('field')
+        self.assertEqual(field.check(), [
+            Error(
+                "'choices' must be an iterable containing (actual value, "
+                "human readable name) tuples.",
+                obj=field,
+                id='fields.E005',
+            ),
+        ])
+
     def test_iterable_of_iterable_choices(self):
         class ThingItem:
             def __init__(self, value, display):
@@ -183,6 +198,18 @@ class CharFieldTests(TestCase):
             ),
         ])
 
+    def test_choices_named_group(self):
+        class Model(models.Model):
+            field = models.CharField(
+                max_length=10, choices=[
+                    ['knights', [['L', 'Lancelot'], ['G', 'Galahad']]],
+                    ['wizards', [['T', 'Tim the Enchanter']]],
+                    ['R', 'Random character'],
+                ],
+            )
+
+        self.assertEqual(Model._meta.get_field('field').check(), [])
+
     def test_bad_db_index_value(self):
         class Model(models.Model):
             field = models.CharField(max_length=10, db_index='bad')