WordCamp GR 2019 – Confidently Testing WordPress – Steve Grunwell

https://stevegrunwell.github.io/confidently-testing-wordpress/#/

Testing Fundamentals

Automated Testing

• Reduces time + chance of human error
• Easily reproducible
• Gateway to CI/CD

Test Types

• Unit – Test the smallest possible unit of an app. Often a single function
• Integration – How individual components interact
• End-to-End(E2E) – An entire path through an application

Automated Testing Pyramid

ROI for Testing

System Under Test (SUT)

• The system we’re currently testing:
  • A single method
  • A class
  • A whole feature

WordPress Testing is Complicated

• Tightly-coupled system
• Difficult to test anything in true isolation

Testing Toolbox

PhpUnit – https://phpunit.de/

Structure

• Test Suite – Collection of test classes
• Test Class (class) – Collection of test methods
• Test Case (method) – A single scenario to be tested

Assertions

• True or False
• Equality
• Verify Contents – contains, regular expression matching
• Negative Assertions

Test Doubles

Replacing actual systems with test versions.

• Stub out/mock an API
• Return known values

Mockery – popular library for creating test doubles

PhpUnit Markup Assertions – Assertions powered by DOMDocument

WP Core Test Suite

Scaffolding Out Test Suite

Generate test scaffolding via WP-CLI

What Do We Get?

• phpunit.xml.dist
• .phpcs.xml.dist
• .travis.yml
• bin/install-wp-tests.sh
• tests/bootstrap.php
• tests/test-sample.php

What We Don’t Get

• Composer

Bootstrap File

1. Locate the WordPress installation
2. Gain access to the tests_add_filter() function.
3. Load the main plugin file.
4. Bootstrap WordPress core.

Base Test Class

• HPUnit\Framework\TestCase
• WP_UnitTestCase

Fixtures

@Group

Data Providers

• Methods
• @testWith

Factories (WordPress)

Generate users, posts, and more for testing.

• factory->post->create()
• factory->post->create_and_get()
• factory->post->create_many()

Impersonating Users (WordPress)

Act as users with different roles & capabilities

go_to() (WordPress)

Change the current page context.

Checking for WP_ERRORs

Was the response an instance of WP_ERROR?

Writing Tests

Arrange – Act – Assert

• Arrange – Set up the scenario
• Act – Execute the code
• Assert – Verify things happened as you expected

Testing Permissions

Registering a Custom Post Type

Testing Hooks

Testing Output

Stubbing HTTP Requests

Basic Test-Driven Development (TDD)

Basic Workflow

1. Write a failing test to describe the functionality or behavior (Red)
2. Write the code to make the test pass (Green)
3. Refactor, rinse, repeat (Refactor)

Regression Tests