django/tests/db_functions/test_cast.py

from django.db import models
from django.db.models.expressions import Value
from django.db.models.functions import Cast
from django.test import TestCase, ignore_warnings, skipUnlessDBFeature

from .models import Author


class CastTests(TestCase):
    @classmethod
    def setUpTestData(self):
        Author.objects.create(name='Bob', age=1, alias='1')

    def test_cast_from_value(self):
        numbers = Author.objects.annotate(cast_integer=Cast(Value('0'), models.IntegerField()))
        self.assertEqual(numbers.get().cast_integer, 0)

    def test_cast_from_field(self):
        numbers = Author.objects.annotate(cast_string=Cast('age', models.CharField(max_length=255)),)
        self.assertEqual(numbers.get().cast_string, '1')

    # Silence "Truncated incorrect CHAR(1) value: 'Bob'".
    @ignore_warnings(module='django.db.backends.mysql.base')
    @skipUnlessDBFeature('supports_cast_with_precision')
    def test_cast_to_char_field_with_max_length(self):
        names = Author.objects.annotate(cast_string=Cast('name', models.CharField(max_length=1)))
        self.assertEqual(names.get().cast_string, 'B')

    def test_cast_to_integer(self):
        for field_class in (
            models.IntegerField,
            models.BigIntegerField,
            models.SmallIntegerField,
            models.PositiveIntegerField,
            models.PositiveSmallIntegerField,
        ):
            with self.subTest(field_class=field_class):
                numbers = Author.objects.annotate(cast_int=Cast('alias', field_class()))
                self.assertEqual(numbers.get().cast_int, 1)

    def test_cast_from_python(self):
        numbers = Author.objects.annotate(cast_float=Cast(0, models.FloatField()))
        self.assertEqual(numbers.get().cast_float, 0.0)