It was the best of code,

It was the worst of code

Technical Debt

• Poor abstractions
• Insufficient namespacing
• Singletons and other anti-patterns

Integration Testing

• Database interaction
• Remote APIs
• Micro-services
• Downstream consumers

Regression Testing

• Customers will report bugs in your application
• A large development team will re-introduce fixed bugs
• Tests can help ensure these bugs don't derail your project

Guilt

I once worked with a developer who ...

WordPress + Testing = ?

• Not many people test their WordPress code
• Core, however, requires testing

Two Ways to Test

• Use the WordPress Core testing framework
• Mock your dependency on WordPress with WP_Mock

Core Test Framework

Core Framework: History

• Originally by Nikolay Bachiyski in 2011
• Officially adopted in 2012 (Test Trac #42)

Core Framework: Coverage

• The entire WordPress API is available
• Data is written to and read from MySQL
• All new code for core must have tests

Core Framework: Goals

The Core Framework aims to test the entire WordPress stack

Core Framework: Example

class Importer {
  /**
   * @var Array Mapping of MT usernames to WordPress user IDs
   */
  private $mtnames = array();

  /**
   * Check that the author exists within WordPress and, if not, create it.
   *
   * @param String $author
   *
   * @return int|\WP_Error
   */
  public function checkauthor( $author ) {
    $pass = wp_generate_password();
    if ( ! isset( $this->mtnames[ $author ] ) ) {
      $user_id = wp_create_user( $author, $pass );
      $this->mtnames[ $author ] = $user_id;
    } else {
      $user_id = $this->mtnames[ $author ];
    }

    return $user_id;
  }
}

Core Framework: Example

/**
 * Make sure new authors are created in WordPress
 */
public function test_checkauthor() {
  $command = new Importer();

  // First author
  $mary_id = $command->checkauthor( 'maryshelley' );
  $mary = \get_user_by( 'id', $mary_id );
  $this->assertEquals( 'maryshelley', $mary->user_login );

  // Second author
  $jane_id = $command->checkauthor( 'janeausten' );
  $this->assertNotEquals( $mary_id, $jane_id );

  // Repeat first
  $mary_redux = $command->checkauthor( 'maryshelley' );
  $this->assertEquals( $mary_id, $mary_redux );
}

WP_Mock

WP_Mock: History

• Originally by me in 2013
• Adopted by 10up and TechCrunch

WP_Mock: Coverage

• APIs are not available unless you define them
• No external services/integrations are used
• Every class/namespace can be tested separately

WP_Mock: Goals

WP_Mock tests only your code, not its environment

WP_Mock: Example

class Importer {
  /**
   * @var Array Mapping of MT usernames to WordPress user IDs
   */
  private $mtnames = array();

  /**
   * Check that the author exists within WordPress and, if not, create it.
   *
   * @param String $author
   *
   * @return int|\WP_Error
   */
  public function checkauthor( $author ) {
    $pass = wp_generate_password();
    if ( ! isset( $this->mtnames[ $author ] ) ) {
      $user_id = wp_create_user( $author, $pass );
      $this->mtnames[ $author ] = $user_id;
    } else {
      $user_id = $this->mtnames[ $author ];
    }

    return $user_id;
  }
}

WP_Mock: Example

/**
 * Make sure new authors are created in WordPress
 */
public function test_checkauthor() {
  \WP_Mock::wpFunction( 'wp_generate_password', array(
    'times'  => 3,
    'return' => 'password',
  ) );

  \WP_Mock::wpFunction( 'wp_create_user', array(
    'times'           => 2,
    'return_in_order' => array( 1, 2 ),
  ) );

  $command = new Importer();

  // First author
  $mary_id = $command->checkauthor( 'maryshelley' );
  $this->assertEquals( 1, $mary_id );

  // Second author
  $jane_id = $command->checkauthor( 'janeausten' );
  $this->assertNotEquals( $mary_id, $jane_id );

  // Repeat first
  $mary_redux = $command->checkauthor( 'maryshelley' );
  $this->assertEquals( $mary_id, $mary_redux );
}