WordPress API Mocking Framework

First, add WP Mock as a dev-dependency with Composer:

composer require --dev 10up/wp_mock:dev-master

Then, make sure your bootstrap file is loading the composer autoloader:

require_once 'vendor/autoload.php';

Finally, register calls inside your test class to instantiate and clean up the WP_Mock object:

class MyTestClass extends PHPUnit_Framework_TestCase {
    public function setUp() {
        \WP_Mock::setUp();
    }

    public function tearDown() {
        \WP_Mock::tearDown();
    }
}

Write your tests as you normally would. If you desire specific responses from WordPress API calls, wire those specifically.

class MyTestClass extends PHPUnit_Framework_TestCase {
    public function setUp() {
        \WP_Mock::setUp();
    }

    public function tearDown() {
        \WP_Mock::tearDown();
    }

    /**
     * The regular `get_the_content()` function is supposed to apply the 'the_content' filter to `post_content`.
     * This test verifies that is the case.
     */
    public function test_content_filter() {
        \WP_Mock::onFilter( 'the_content' )->with( 'Windows Rocks!' )->reply( 'Apple Rocks!' );

        $post = new stdClass;
        $post->post_content = 'Windows Rocks!';
        setup_postdata( $post );

        $content = get_the_content();

        $this->assertEquals( 'Apple Rocks!', $content );
    }

    /**
     * Our special_action function must actually invoke the 'special_action' action when it's done.
     * function special_action() {
     *     // ... do stuff
     *     do_action( 'special_action' );
     * }
     */
    public function test_method_has_action() {
        \WP_Mock::expectAction( 'special_action' );

        // If this function does not call `do_action( 'special_action' )`, the test will fail.
        special_action();
    }

    /**
     * Our init function must add an action to save_post and a filter to the_content
     * function special_init() {
     *     add_action( 'save_post', 'special_save_post', 10, 2 );
     *     add_filter( 'the_content', 'special_the_content' );
     * }
     */
    public function test_init() {
        \WP_Mock::expectActionAdded( 'save_post', 'special_save_post', 10, 2 );
        \WP_Mock::expectFilterAdded( 'the_content', 'special_the_content' );
        // If this function does not add the action and filter we expect with the correct priority and argument count, the test will fail.
        special_init();
    }
}

When you need to mock core WordPress functions, such as get_post(), use \WP_Mock::wpFunction():

    public function test_uses_get_post() {
        global $post;
        $post = new \stdClass;
        $post->ID = 42;
        $post->special_meta = '<p>I am on the end</p>';
        \WP_Mock::wpFunction( 'get_post', array(
            'times' => 1,
            'args' => array( $post->ID ),
            'return' => $post,
        ) );
        // Let's say our function gets the post and appends a value stored in 'special_meta' to the content
        $results = special_the_content( '<p>Some content</p>' );
        // In addition to failing if this assertion is false, the test will fail if get_post is not called with the arguments above
        $this->assertEquals( '<p>Some content</p><p>I am on the end</p>', $results );
    }

\WP_Mock::wpFunction() will dynamically define the function for you if necessary. Generally, it's best to let it do so, just in case we need to change the internal API, your mocks will continue to work. If you really want to define your own function mocks, they should always end with this line:

return \WP_Mock\Handler::handle_function( __FUNCTION__, func_get_args() );

\WP_Mock::wpFunction()'s second parameter accepts a few arguments as an associative array:

• times: Defines expectations for the number of times a function should be called. The default is 0 or more times. To expect the function to be called an exact amount of times, set times to a non-negative numeric value. To specify that the function should be called a minimum number of times, use a string with the minimum followed by '+' (e.g. '3+' means 3 or more times). Append a '-' to indicate a maximum number of times a function should be called (e.g. '3-' means no more than 3 times). To indicate a range, use '-' between two numbers (e.g. '2-5' means at least 2 times and no more than 5 times).
• return: Defines the value (if any) that the function should return. If you pass a \Closure as the return value, the function will return whatever the Closure's return value is.
• return_in_order: Use this if your function will be called multiple times in the test but needs to have different return values. Set this to an array of return values. Each time the function is called, it will return the next value in the sequence until it reaches the last value, which will become the return value for all subsequent calls. For example, if I am mocking is_single(), I can set return_in_order to array( false, true ). The first time is_single() is called it will return false. The second and all subsequent times it will return true. Setting this value overrides 'return', so if you set both, 'return' will be ignored.
• return_arg: Use this to specify that the function should return one of its arguments. return_arg should be the position of the argument in the arguments array, so 0 for the first argument, 1 for the second, etc. You can also set this to true, which is equivalent to 0. This will override both return and return_in_order.
• args: Use this to set expectations about what the arguments passed to the function should be. This value should always be an array with the arguments in order. Like with return, if you use a \Closure, its return value will be used to validate the argument expectations. Also, you can indicate that the argument can be any value of any type by using '*'. WP_Mock has several helper functions to make this feature more flexible. The are static methods on the \WP_Mock\Functions class. They are:
  • Functions::type( $type ): Expects an argument of a certain type. This can be any core PHP data type (string, int, resource, callable, etc.) or any class or interface name.
  • Functions::anyOf( $values ): Expects the argument to be any value in the $values array

So, for example, if I am expecting get_post_meta() to be called, the 'args' array might look something like this:

array( $post->ID, 'some_meta_key', true )