django/tests/db_functions/text/test_left.py

28 lines
1.2 KiB
Python

from django.db.models import CharField, Value
from django.db.models.functions import Left, Lower
from django.test import TestCase
from ..models import Author
class LeftTests(TestCase):
@classmethod
def setUpTestData(cls):
Author.objects.create(name='John Smith', alias='smithj')
Author.objects.create(name='Rhonda')
def test_basic(self):
authors = Author.objects.annotate(name_part=Left('name', 5))
self.assertQuerysetEqual(authors.order_by('name'), ['John ', 'Rhond'], lambda a: a.name_part)
# If alias is null, set it to the first 2 lower characters of the name.
Author.objects.filter(alias__isnull=True).update(alias=Lower(Left('name', 2)))
self.assertQuerysetEqual(authors.order_by('name'), ['smithj', 'rh'], lambda a: a.alias)
def test_invalid_length(self):
with self.assertRaisesMessage(ValueError, "'length' must be greater than 0"):
Author.objects.annotate(raises=Left('name', 0))
def test_expressions(self):
authors = Author.objects.annotate(name_part=Left('name', Value(3), output_field=CharField()))
self.assertQuerysetEqual(authors.order_by('name'), ['Joh', 'Rho'], lambda a: a.name_part)