1131056 - Add tests for webactivities code in fireplace

Status: RESOLVED WONTFIX

(Marketplace Graveyard :: Code Quality, defect, P3)

Description

[Mathieu Pillard [:mat]]

Fireplace's webactivities.js is not covered by unit tests.

With the current testing architecture it can be tricky to do - I tried to do it as part of bug 1122272 but it turned out to be slightly more complicated than I had anticipated so I am opening this bug instead.

Random notes:
- We should expose expose handleActivity() method and we should test it independently
- Testing mozSetMessageHandler and message passing should be done too
- We need to figure out a way to test this without actually navigating away. Sadly, the modules that webactivities.js requires all use `z` module in various ways, and with our current testing architecture, it's difficult to mock just z.page.trigger() without affecting those modules.
- We could also add integration tests, triggering various activities/messages and looking where we end up navigating, without mocking anything.