Fixed #26610 -- Added CITextField to contrib.postgres.

tests/postgres_tests/test_citext.py

@@ -0,0 +1,30 @@
+"""
+The citext PostgreSQL extension supports indexing of case-insensitive text
+strings and thus eliminates the need for operations such as iexact and other
+modifiers to enforce use of an index.
+"""
+from django.db import IntegrityError
+
+from . import PostgreSQLTestCase
+from .models import CITextTestModel
+
+
+class CITextTestCase(PostgreSQLTestCase):
+
+    @classmethod
+    def setUpTestData(cls):
+        CITextTestModel.objects.create(name='JoHn')
+
+    def test_equal_lowercase(self):
+        """
+        citext removes the need for iexact as the index is case-insensitive.
+        """
+        self.assertEqual(CITextTestModel.objects.filter(name='john').count(), 1)
+
+    def test_fail_case(self):
+        """
+        Creating an entry for a citext-field which clashes with an existing
+        value isn't allowed.
+        """
+        with self.assertRaises(IntegrityError):
+            CITextTestModel.objects.create(name='John')