if ($entity instanceof EditorAttributes) {
    // ....
}

class FooTest extends PHPUnitFrameworkTestCase
{
    public function testFoo()
    {
        $mock = $this->getMock('EditorAttributes');
        $this->assertTrue($mock instanceof EditorAttributes);
    }
}

class FooTest extends PHPUnitFrameworkTestCase
{
    public function testFoo()
    {
        $mock = $this->getMock(['EditorAttributes', 'ReaderAttributes']);
        $this->assertTrue($mock instanceof EditorAttributes);
        $this->assertTrue($mock instanceof ReaderAttributes);
    }
}