Add tests for writable cache dir

<?php

/*

Plugin Name: Test Plugin

Description: Assists in the testing of some scenarios

*/

add_action( 'rest_api_init', function() {

	register_rest_route( 'test/v1', '/write-cache', array(

		'methods' => WP_REST_Server::READABLE,

		'callback' => function($request) {

			if ( !isset($request['file']) ) {

				return new WP_Error('Missing param file');

			}

			$file = WP_CONTENT_DIR . "/cache/{$request['file']}";

			file_put_contents($file, "Generated file");

			return rest_ensure_response( "Cache file created" );

		},

		'args' => array(

			'file' => array(

				'description' => 'File to touch on the server host',

				'type' => 'string',

			)

		)

	));

});

/* register_activation_hook( __FILE__, function() { */

/* 	if ( !defined('WP_CLI') && $_SERVER['REQUEST_URI'] == '/test-cache' ) { */

/* 		$file = WP_CONTENT_DIR . "/cache/${_GET['file']}"; */

/* 		file_put_contents($file, "Generated file"); */

/* 		wp_die("Cache file created", 200); */

/* 	} */

/* }); */

@wip

Feature: Page cache directory

	Ensure that the page cache directory at WP_CONTENT_DIR/cache is writable for

	plugins, but is not served by the server.

	Scenario: After the entrypoint has completed, there is a writable cache dir

		Given the site is not running

		And test-cache.php is mounted in /app/wp-content/mu-plugins/

		When the site is started

		And /wp-json/test/v1/write-cache?file=foo.txt is requested

		Then OK is returned

		And /app/wp-content/cache/foo.txt exists in the backend

	Scenario: The contents of the cache dir are not served by the proxy

		Given /app/wp-content/cache/foo exists in the backend

		When /wp-content/cache/foo is requested

		Then Not Found is returned

		assert site.backend.cli(addon.value, "is-active", name, query=True) == status.value

@then("{path:Path} exists in the {container_name}")

def check_file_exists(context: Context, path: Path, container_name: str) -> None:

	"""

	Check a file exists in the named container

	"""

	site = use_fixture(site_fixture, context)

	container = getattr(site, container_name)

	assert container.run(["sh", "-c", f"test -e {path}"]).returncode == 0, \

		f"{path} not found in the {container_name}"

@then("the email address of {user} is \"{value}\"")

@then("the email address of {user} is '{value}'")

def is_user_email(context: Context, user: str, value: str) -> None: