[PYTHON] When writing a test using DB with django, you may be able to do it faster by using `setUpTestData ()`

When writing a test using DB with django, you may be able to do it faster by using setUpTestData ()

When writing a test using DB in django, you may be able to do it faster by using setUpTestData ().

setUpTestData()？

setUpTestData () is usually setUp () for each method This is to perform model initialization etc. on a class-by-class basis. (It might be a little interesting if you take a look at the internal implementation.)

Of course, being initialized on a class-by-class basis means that it will only be called once, so you need to be careful about things that update their status.

Example

For example, suppose you write a test for a search for django.contrib.auth.models.User in Texto. (There is no particular reason to choose ʻUser`. It's just a mess of defining the model.)

Calling setUp () every time

In the following test cases, User models are generated for the number of test methods. slow.

class Tests(TestCase):
    def setUp(self):
        from django.contrib.auth.models import User
        for i in range(110):
            User.objects.create_superuser("admin{}".format(i), "myemail{}@example.com".format(i), '')

    def test_query(self):
        from django.contrib.auth.models import User
        with self.assertNumQueries(1):
            actual = User.objects.filter(username__startswith="admin1").count()
            self.assertEqual(actual, 11)

    def test_query1(self):
        from django.contrib.auth.models import User
        with self.assertNumQueries(1):
            actual = User.objects.filter(username__startswith="admin1").count()
            self.assertEqual(actual, 11)

    def test_query2(self):
        from django.contrib.auth.models import User
        with self.assertNumQueries(1):
            actual = User.objects.filter(username__startswith="admin1").count()
            self.assertEqual(actual, 11)

Using setUpTestData ()

class Tests(TestCase):
    @classmethod
    def setUpTestData(cls):
        from django.contrib.auth.models import User
        for i in range(100):
            User.objects.create_superuser("admin{}".format(i), "myemail{}@example.com".format(i), '')

    def test_query(self):
        from django.contrib.auth.models import User
        with self.assertNumQueries(1):
            actual = User.objects.filter(username__startswith="admin1").count()
            self.assertEqual(actual, 11)

    def test_query1(self):
        from django.contrib.auth.models import User
        with self.assertNumQueries(1):
            actual = User.objects.filter(username__startswith="admin1").count()
            self.assertEqual(actual, 11)

    def test_query2(self):
        from django.contrib.auth.models import User
        with self.assertNumQueries(1):
            actual = User.objects.filter(username__startswith="admin1").count()
            self.assertEqual(actual, 11)

Comparison of execution time

Let's compare the execution time. The more setUp () is called for the number of test methods, the slower it will be, and the ratio of results is not very meaningful. Since there are 3 test methods, it takes about 3 times longer to generate the data with setUp ().

If you want to try it out, you can check it with the following gist.

https://gist.github.com/podhmo/ffc6f96e4688dfb53810f4e4d6ba4d92