实际上，您不能使用WP_UnitTestCase, 因为在bootstrap.php 您已经将插件加载为mu-plugin.

我建议您测试插件激活：调用do_action(\'activate_\' . FULL_ABSPATH_TO_YOUR_PLUGIN_PHP), 哪里FULL_ABSPATH_TO_YOUR_PLUGIN_PHP 将类似于：var/www/html/wordpress/wp-content/plugins/hello-world/hello-world.php

在本例中hello-world 插件吊销指定用户激活时的功能：

class ActivationEventTest extends WP_UnitTestCase {

    const PLUGIN_BASENAME = \'var/www/html/wordpress/wp-content/plugins/hello-world/hello-world.php\';

    public function testActivateWithSupport() {
        $this->factory()->user->create( [
            \'user_email\' => \'[email protected]\',
            \'user_pass\'  => \'reallyheavypasword\',
            \'user_login\' => \'hello\',
            \'user_role\'  => 4,
            \'role\'       => 4
        ] );

        do_action( \'activate_\' . static::PLUGIN_BASENAME );

        $user = get_user_by( \'login\', \'hello\' );
        $this->assertEmpty( $user->caps );
        $this->assertEmpty( $user->roles );
    }
}

使用核心WordPress测试套件测试插件激活/安装和卸载可以更容易、更正确地完成these additional utilities. 他们主要关注的是测试卸载，但也测试激活/安装。这是其中的示例测试用例，并显示了如何测试安装和卸载：

<?php

/**
 * Test uninstallation.
 */

/**
 * Plugin uninstall test case.
 *
 * Be sure to add "@group uninstall", so that the test will run only as part of the
 * uninstall group.
 *
 * @group uninstall
 */
class My_Plugin_Uninstall_Test extends WP_Plugin_Uninstall_UnitTestCase {

    //
    // Protected properties.
    //

    /**
     * The full path to the main plugin file.
     *
     * @type string $plugin_file
     */
    protected $plugin_file;

    //
    // Public methods.
    //

    /**
     * Set up for the tests.
     */
    public function setUp() {

        // You must set the path to your plugin here.
        $this->plugin_file = dirname( dirname( __FILE__ ) ) . \'/myplugin.php\';

        // Don\'t forget to call the parent\'s setUp(), or the plugin won\'t get installed.
        parent::setUp();
    }

    /**
     * Test installation and uninstallation.
     */
    public function test_uninstall() {

        /*
         * First test that the plugin installed itself properly.
         */

        // Check that a database table was added.
        $this->assertTableExists( $wpdb->prefix . \'myplugin_table\' );

        // Check that an option was added to the database.
        $this->assertEquals( \'default\', get_option( \'myplugin_option\' ) );

        /*
         * Now, test that it uninstalls itself properly.
         */

        // You must call this to perform uninstallation.
        $this->uninstall();

        // Check that the table was deleted.
        $this->assertTableNotExists( $wpdb->prefix . \'myplugin_table\' );

        // Check that all options with a prefix was deleted.
        $this->assertNoOptionsWithPrefix( \'myplugin\' );

        // Same for usermeta and comment meta.
        $this->assertNoUserMetaWithPrefix( \'myplugin\' );
        $this->assertNoCommentMetaWithPrefix( \'myplugin\' );
    }
}

至于你的测试为什么会失败，我不确定。要调试它，您需要查看该错误的来源activate_plugin(); 插件文件检查的哪一部分失败了？像xdebug这样的工具对于这类事情来说是非常宝贵的。如果您没有为正在使用的PHP构建安装xdebug（您可能应该得到它），那么您必须通过查看activate_plugin() 并查看错误的来源。