Simplified choices iterators in tests.model_fields.models.

tests/model_fields/models.py

@@ -50,27 +50,12 @@ class Whiz(models.Model):
     c = models.IntegerField(choices=CHOICES, null=True)
 
 
-class Counter:
-    def __init__(self):
-        self.n = 1
-
-    def __iter__(self):
-        return self
-
-    def __next__(self):
-        if self.n > 5:
-            raise StopIteration
-        else:
-            self.n += 1
-            return (self.n, 'val-' + str(self.n))
-
-
 class WhizIter(models.Model):
-    c = models.IntegerField(choices=Counter(), null=True)
+    c = models.IntegerField(choices=iter(Whiz.CHOICES), null=True)
 
 
 class WhizIterEmpty(models.Model):
-    c = models.CharField(choices=(x for x in []), blank=True, max_length=1)
+    c = models.CharField(choices=iter(()), blank=True, max_length=1)
 
 
 class BigD(models.Model):