Split model_fields tests into different files.

tests/model_fields/test_textfield.py

@@ -0,0 +1,25 @@
+from django.db import models
+from django.test import TestCase
+
+from .models import Post
+
+
+class TextFieldTests(TestCase):
+
+    def test_max_length_passed_to_formfield(self):
+        """
+        TextField passes its max_length attribute to form fields created using
+        their formfield() method.
+        """
+        tf1 = models.TextField()
+        tf2 = models.TextField(max_length=2345)
+        self.assertIsNone(tf1.formfield().max_length)
+        self.assertEqual(2345, tf2.formfield().max_length)
+
+    def test_to_python(self):
+        """TextField.to_python() should return a string."""
+        f = models.TextField()
+        self.assertEqual(f.to_python(1), '1')
+
+    def test_lookup_integer_in_textfield(self):
+        self.assertEqual(Post.objects.filter(body=24).count(), 0)