8 – How to do the functional test of a module within a subsite?

I tried to perform a simple test of a module located in a subsite (Drupal multisite), but when the test looks for the module to activate it, it can not be found if I move the module from the sub site to the module folder that is in the root of the installation if you find it.

Is it possible to do the tests from the subsite? Or do I necessarily have to move them to the root folder?

user = $ this-> drupalCreateUser (['administer site configuration']);
$ this-> drupalLogin ($ this-> user);

/ **
* Tests loading the home page with a response of 200.
* /
public function testLoad () {
$ this-> drupalGet (Url :: fromRoute (& # 39;& # 39;));
$ this-> assertSession () -> statusCodeEquals (200);


Thank you