gistfile1.php

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

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

    public function test_content_filter() {
        \WP_Mock::onFilter( 'the_content' )->with( 'Windows Rocks!' )->reply( 'Apple Rocks!' );

        $content = 'Windows Rocks!';

        $filtered = apply_filters( 'the_content', $content );

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

    /**
     * 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() {
        $hook_intercept = \Mockery::mock( 'intercept' );
        $hook_intercept->shouldReceive( 'intercepted' );
        \WP_Mock::onAction( 'special_action' )->with( null )->perform( array( $hook_intercept, 'intercepted' ) );

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