django/tests/db_functions/text/test_repeat.py

from django.db import connection
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')
        none_value = '' if connection.features.interprets_empty_strings_as_nulls else None
        tests = (
            (Repeat('name', 0), ''),
            (Repeat('name', 2), 'JohnJohn'),
            (Repeat('name', Length('alias'), output_field=CharField()), 'JohnJohnJohn'),
            (Repeat(Value('x'), 3, output_field=CharField()), 'xxx'),
            (Repeat('name', None), none_value),
            (Repeat('goes_by', 1), none_value),
        )
        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)