Build failing with timeout after changing the way to open external browser in tests


I changed the way to open external browser from my VS Code extension.
I switched from using opn to using the internal dedicated VS Code API.
With opn, the build is working fine.
With VS Code API, the tests are still passing but at the end the build stays blocked and it finally timeout.
I’m unable to reproduce the issue locally.
I tried to specify Chrome and Firefox addons with same results.
What can cause Travis to not go to the next step of the build? finish the build? How to investigate on that?


failing build:

slight modification of my code: