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Documentation for WP PHPUnit
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WP PHPUnit Documentation



WP PHPUnit is the WordPress PHPUnit unit test library included in the WordPress core develop repository, made installable via Composer. The primary goal is to make getting up and running with your tests much faster. Rather than tracking down a script or copying from project to project, you have a single package to add to your development dependencies.


The core PHPUnit test library is a fundamental library for writing PHPUnit tests with WordPress. Historically, it has only been available to install via SVN checkout, usually from a script. As a PHP dependency it only makes sense that this should be installable via Composer with the rest of your dependencies.

One obstacle to achieving this is due to a hardcoded required placement of the wp-tests-config.php file by the library's bootstrap.php. When including as a library in a project, it expects the tests config file to be in the parent directory of the library's includes directory.

/ (library root)
├── data
├── includes
│   ├── bootstrap.php
│   ├── factory.php
│   ├── functions.php
│   ├── install.php
│   └── ...
└── wp-tests-config.php

Normally this file would not be editable installed as a Composer dependency, because files within its vendor directory are not intended to be modified.

WP PHPUnit solves this by including this file in the package source which acts as a kind of proxy to your "real" tests config file, which can be wherever you wish.


Install the latest version

composer require wp-phpunit/wp-phpunit --dev

Because WP PHPUnit is a simple versioned subset mirror of WordPress core, it shares the same tag as the version it was built from.

Install the version for a specific version of WordPress

composer require wp-phpunit/wp-phpunit:4.9.1 --dev

PHPUnit Compatibility

The library is compatible with PHPUnit 3.6+, 4, 5, and support for newer versions of PHPUnit have been added since.

  • Support for PHPUnit 6 was added in WordPress 4.8.
  • Support for PHPUnit 7 was added in WordPress 5.1.
  • Support for PHPUnit 8 is not yet available, but in the works (see #46149).


The only configuration necessary for WP PHPUnit is to set the location to your real tests config file as an environment variable.

There are many ways to do this, but the easiest way is to define this in your phpunit.xml file for your project!

    <!-- ... -->

        <env name="WP_PHPUNIT__TESTS_CONFIG" value="tests/wp-config.php" />

    <!-- ... -->

Alternatively, you could set this in PHP anywhere before the includes/bootstrap.php file is required:

putenv( 'WP_PHPUNIT__TESTS_CONFIG=path/to/wp-tests-config.php' );

Create a wp-tests-config.php file

curl -sSL -o wp-tests-config.php

Modify this file as necessary as you will likely want to commit it to version control. Be sure not to hardcode any sensitive data into it. Instead you may consider using something like phpdotenv to set your keys and secrets in a .env file which are then loaded as environment variables.

Table Prefix (optional)

You may also configure the table prefix which you want to use for your tests.

This is configurable by setting the WP_PHPUNIT__TABLE_PREFIX environment variable. If set, this will take precedence over what is set in your tests config file. If not, and the $table_prefix variable is not set in your tests config file then it will use wptests_ as a fallback.


Updating the default bootstrap.php file to use WP PHPUnit

--- /tmp/tests/bootstrap-before.php
+++ /tmp/tests/bootstrap-after.php
@@ -5,7 +5,9 @@
-$_tests_dir = getenv( 'WP_TESTS_DIR' );
+// Composer autoloader must be loaded before WP_PHPUNIT__DIR will be available
+require_once dirname( dirname( __FILE__ ) ) . '/vendor/autoload.php';
+$_tests_dir = getenv( 'WP_TESTS_DIR' ) ?: getenv( 'WP_PHPUNIT__DIR' );
 if ( ! $_tests_dir ) {
     $_tests_dir = rtrim( sys_get_temp_dir(), '/\\' ) . '/wordpress-tests-lib';

Complete Working Examples

WP PHPUnit in the Wild

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