Reorganized text db function tests.

tests/db_functions/text/test_repeat.py

@@ -0,0 +1,24 @@
+from django.db.models import CharField, Value
+from django.db.models.functions import Length, Repeat
+from django.test import TestCase
+
+from ..models import Author
+
+
+class RepeatTests(TestCase):
+    def test_basic(self):
+        Author.objects.create(name='John', alias='xyz')
+        tests = (
+            (Repeat('name', 0), ''),
+            (Repeat('name', 2), 'JohnJohn'),
+            (Repeat('name', Length('alias'), output_field=CharField()), 'JohnJohnJohn'),
+            (Repeat(Value('x'), 3, output_field=CharField()), 'xxx'),
+        )
+        for function, repeated_text in tests:
+            with self.subTest(function=function):
+                authors = Author.objects.annotate(repeated_text=function)
+                self.assertQuerysetEqual(authors, [repeated_text], lambda a: a.repeated_text, ordered=False)
+
+    def test_negative_number(self):
+        with self.assertRaisesMessage(ValueError, "'number' must be greater or equal to 0."):
+            Repeat('name', -1)