As seen today while implementing the logic for opening new browser windows in Firefox, the send_keys() method is broken when capital letters are contained in the string. Here an example: marionette.%window_element%.send_keys(*[u'\ue009', u'N']) This is Ctrl+N and should open a new browser window. But sending this combination does nothing, because as Chris told me, the shift key is getting activated internally. As long as the shift key is not explicitly requested, it should not be used.

This happens quite explicitly here: https://hg.mozilla.org/mozilla-central/annotate/34e2d2bd7ec4/testing/marionette/marionette-sendkeys.js#l205 I re-instated that when working on sendkeys due to the previous behavior, which was similar.

How would a user do `N` without pressing pressing the shift key?

So for the shortcuts Firefox gives us command keys with capital letters, as shown above. If we have to keep the current behavior and I see now why, we may have to force our send_shortcut() method to lowercase the command key. Given that the capitalization of a command key doesn't matter, we should be fine.

The key capitalization, as whimboo points out, doesn't matter for this case. Closing since this is desired behaviour since it is impossible to do `N` without a shift or setting capslock (and that's still `n`).

Btw your fix on bug 1255806 fixed this problem.