Testing certain branch in the cloud accessible for developers

It should be possible to run all tests in the cloud as a merge-precondition for any pull request. Also it should be possible for any developer run tests at the any step developer needs and on any branch needed. 

So it means some infrastructure/architecture/functionality should be set up that allow to do that independently for any branch and any point of time via single command / button / hook, so that this will allow to unblock developers' workstations from being 'freezed' during the tests are running and prevent merging pull requests on Bitbucket