Since MopaBootstrapBundle uses Symfony Form extensions you can test them as usual Symfony Forms.
The way of testing them is clearly described in a Cookbook.
The only difference between testing pure Symfony forms and MopaBootstrap Forms is the fact that you need to use Mopa\Bundle\BootstrapBundle\Tests\Form\TypeTestCase instead of Symfony\Component\Form\Test\TypeTestCase
You can see an example in MopaBootstrapSandboxBundle