This are the two tests that I think we need. Please extend as you feel is appropriate.
In #1137920: Fix toolbar on small screen sizes and redesign toolbar for desktop you have been saying that "benjifisher is working on" this issue. Not yet. I will get to it soon. (Too many comments and too many followers on that issue, and I do not want to add to the overload.)
If anyone else wants to work on it, I promise to post a comment when I start. I hate duplicated effort.
I was looking for a simpletest from when the toolbar went in, that tested for icons, so I could copy it for this language issue:#1848552: Toolbar icons disappear with translated menu
It sounds like there are not tests yet?
I am working on rewriting hook_toolbar() in #1847198: Update the structure returned by hook_toolbar(). I will submit patches here when that work is done. For now, I have set up a sandbox project for a testing/example module for the toolbar hooks: http://drupal.org/sandbox/benji/1862108.
The existing tests are being updated as part of #1847198: Update the structure returned by hook_toolbar(). I think it makes sense to wait until that issue is resolved before adding any more, so I am marking this issue Postponed.
According to the discussion in #1532612: Move Examples Project into Drupal core, we should do much more than the tests suggested in the issue summary. We should test every edge case we can imagine and do our best to break the API.
Updated issue summary.
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