How do I generate 1,000 objects in Django and DRF to test?
April 14, 2020
Earlier this week, Isa Buriticá asked me a great question about how to bulk create and test items in a Django test and I wanted to share that information on my website.
Question
I am using Django Rest Framework and I need to test an endpoint with at least 1,000 objects. But putting that in a cycle doesn't seem very optimal to me.
Do you know of any way to create objects in bulk within the tests?
Answer
My go-to library of choice for creating test data, more commonly called “fixtures” in Django tests, is Model Bakery.
With Model Bakery, you can pass in a Django model or model reference, and Bakery will create an object based on that model type.
This fully-baked object includes valid test data so that each required field has the right type of data it needs.
Here is an example, based on their docs:
{% include snippets/src-snippet-example-01.md %}
To create 1,000 categories for a test, we pass the optional _quantity parameter to our baker.make method.
Here is another example based on the docs:
{% include snippets/src-snippet-example-02.md %}
Bonus Answers
Bonus Answer 1: It works well with pytest.fixtures
If you are using pytest and pytest-django, one pattern that I use all the time is to create a series of text fixtures for each of my models that I will be testing with.
tests/fixtures.py
{% include snippets/src-snippet-example-03-fixtures.md %}
pytest fixtures are nice way to reduce the amount of boilerplate code you need for creating and testing objects.
To use one of your new tests fixtures, you pass them in as a method argument and pytest will pass the fixture into the test function.
tests/test_models.py
{% include snippets/src-snippet-example-04-test_models.md %}
For more information about pytest.fixtures, check out the pytest fixtures: explicit, modular, scalable docs.
Bonus Answer 2: It works well for generating test data
Model Bakery also has a prepare method which is useful for creating valid test data for a Django model without saving it to our database.
I use this method often for testing Django Forms and DRF POST methods.
{% include snippets/src-snippet-example-05.md %}
Thanks to Will Vincent for advice on and corrections to a draft of this article.