Unit Testing in WordPress: how to use the factory object in the setUp method

I’ve been writing more unit tests of late and have been running into some interesting issues when working with WordPress plugins.

If you’re just getting started with unit testing I can highly recommend the following articles/turorials/videos to help you along:

• https://pippinsplugins.com/unit-tests-wordpress-plugins-setting-up-testing-suite/
• http://taylorlovett.com/2014/07/04/wp_unittestcase-the-hidden-api/
• https://www.youtube.com/watch?v=84j61_aI0q8

My problem was that I wanted to define a couple of things in the setUp() method in my testing class using the factory() method of WP_UnitTestCase, but $this->factory() was null.

The quick fix was to explicitly call parent::setUp() before attempting to use the factory method in my own class.

This didn’t work:

<?php
class Test_NID_RSS_Importer extends WP_UnitTestCase {

    public $user_id = null;

    public function setUp() {
        $this->user_id = $this->factory->user->create( array( 'user_login' => 'test', 'role' => 'administrator' ) );
    }

    public function test_something() {
        $this->user_id; // Do some tests!
    }

}

But this does:

<?php
class Test_NID_RSS_Importer extends WP_UnitTestCase {

    public $user_id = null;

    public function setUp() {
        parent::setUp(); // Aha!
        $this->user_id = $this->factory->user->create( array( 'user_login' => 'test', 'role' => 'administrator' ) );
    }

    public function test_something() {
        $this->user_id; // Do some tests!
    }

}