roundcubemail/plugins/additional_message_headers/tests/AdditionalMessageHeaders.php

<?php

class AdditionalMessageHeaders_Plugin extends ActionTestCase
{
    public static function setUpBeforeClass(): void
    {
        include_once __DIR__ . '/../additional_message_headers.php';
    }

    /**
     * Test the plugin
     */
    public function test_plugin()
    {
        $rcube  = rcube::get_instance();
        $plugin = new additional_message_headers($rcube->plugins);

        $this->assertInstanceOf('additional_message_headers', $plugin);
        $this->assertInstanceOf('rcube_plugin', $plugin);

        $plugin->init();

        $args = ['message' => new Mail_mime()];

        $result = $plugin->message_headers($args);

        $this->assertSame("MIME-Version: 1.0\r\n", $result['message']->txtHeaders());

        $rcube->config->set('additional_message_headers', ['X-Test' => 'Test']);

        $result = $plugin->message_headers($args);

        $this->assertSame("MIME-Version: 1.0\r\nX-Test: Test\r\n", $result['message']->txtHeaders());
    }
}