Make it easier to write tests for WordPress plugins containing CLI commands

[swissspidy]

Situation:

I'm developing a WordPress plugin that registers some WP-CLI commands. Now I want to write some functional tests for these, ideally by leveraging this identical testing framework as for standalone commands.

In case anyone's wondering, the plugin I'm developing can be found at https://github.com/wearerequired/traduttore.

To run the tests, I need to activate / load the plugin somehow.

One suggestion by Daniel that led me to the right path was creating a ZIP archive and installing that ZIP file. He did this in a plugin once where FeatureContext.php was part of the code base. I obviously can't edit that file because it's now in the wp-cli-tests package.

Alain's suggestion was to use something like this:

Feature: Testing a custom plugin

  Background:
    Given a WP installation
    And these installed and active plugins:
    """
    {RUN_DIR}/packaged_plugin.zip
    """

However, variables are currently not being replaced in the these installed and active plugins step.

Plus, RUN_DIR points to the WordPress directory used for the tests, not the actual repository where my plugin and my ZIP file reside.

Thus, I decided to add a new variable, PROJECT_DIR which aims to be the plugin source directory. That's also where wp-cli/wp-cli-tests is installed using Composer in PROJECT_DIR/vendor/wp-cli/wp-cli-tests.

This way I can use the following scenario:

Feature: Testing a custom plugin

  Background:
    Given a WP installation
    And these installed and active plugins:
    """
    {PROJECT_DIR}/packaged_plugin.zip
    """

[swissspidy]

wearerequired/traduttore#124 is where I'm currently using this PR.

[schlessera]

I think this is a good first step to support this, and the changes generally make sense in any case. However, I think we should ultimately try to make it possible to test a plugin without needing to zip it up first.

[swissspidy]

Oh, absolutely.

I explored that too but quickly ran into problems with the autoloader, getting errors like these (as described in wearerequired/traduttore#124):

Cannot redeclare composerRequiree4cd214cfd5d4f7870ef4ac7c4e1ab20() (previously declared in vendor/composer/autoload_real.php:63) in /private/var/folders/.../wp-cli-test-run-cli.feature.19-5bf18a4fd5de42.86243506/wp-content/plugins/traduttore/vendor/composer/autoload_real.php