Long term, I believe that we should remove the internal/Object.freeze(external) model since legacy addons are not around anymore. In the meantime, I made a minimal test case [0] that reproduces how FxAccounts sets up a mocked internal [1]. If you execute that test you'll notice that "Original implementation" is printed to the console whereas it should be "Mocked implementation". [0] https://pastebin.mozilla.org/9076108 [1] https://searchfox.org/mozilla-central/source/services/fxaccounts/FxAccounts.jsm#309-372

Assigning a reviewer once I confirm this patches fixes my testing problem in bug 1426306.

Comment on attachment 8943106 [details] Bug 1430970 - Fix FxAccounts internal mocking. https://reviewboard.mozilla.org/r/213406/#review219214 yay - I pushed back (and lost) against that cruft and will be happy to see it gone :)

Comment on attachment 8943106 [details] Bug 1430970 - Fix FxAccounts internal mocking. https://reviewboard.mozilla.org/r/213406/#review219530 This is silly, but your changes reduce the net silliness of this code.

Pushed by eoger@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/16d1d6155d1d Fix FxAccounts internal mocking. r=tcsc