.. index::
   pair: Tests ; constraints

.. _tests_constraints:

============================================
Tests **constraints**
============================================

.. seealso::

   - https://docs.djangoproject.com/en/dev/ref/models/constraints
   - https://github.com/django/django/blob/master/docs/ref/models/constraints.txt
   - https://github.com/django/django/blob/master/tests
   - https://github.com/django/django/blob/master/tests/invalid_models_tests/test_models.py


.. contents::
   :depth: 3


class ConstraintsTests(TestCase):
=====================================

.. code-block:: python
   :linenos:


    import unittest

    from django.conf import settings
    from django.core.checks import Error, Warning
    from django.core.checks.model_checks import _check_lazy_references
    from django.db import connection, connections, models
    from django.db.models.functions import Lower
    from django.db.models.signals import post_init
    from django.test import SimpleTestCase, TestCase
    from django.test.utils import isolate_apps, override_settings, register_lookup


    @isolate_apps('invalid_models_tests')
    class ConstraintsTests(TestCase):
        def test_check_constraints(self):
            class Model(models.Model):
                age = models.IntegerField()

                class Meta:
                    constraints = [models.CheckConstraint(check=models.Q(age__gte=18), name='is_adult')]

            errors = Model.check(databases=self.databases)
            warn = Warning(
                '%s does not support check constraints.' % connection.display_name,
                hint=(
                    "A constraint won't be created. Silence this warning if you "
                    "don't care about it."
                ),
                obj=Model,
                id='models.W027',
            )
            expected = [] if connection.features.supports_table_check_constraints else [warn]
            self.assertCountEqual(errors, expected)

        def test_check_constraints_required_db_features(self):
            class Model(models.Model):
                age = models.IntegerField()

                class Meta:
                    required_db_features = {'supports_table_check_constraints'}
                    constraints = [models.CheckConstraint(check=models.Q(age__gte=18), name='is_adult')]

            self.assertEqual(Model.check(databases=self.databases), [])