How to fill tinymce-rails editor with capybara and selenium?
Switching to chrome as described here solved my problem.
Obviously the problem is related with a bug in firefox driver.
Still i think it is a valid question for firefox.
I know that this is an old question but I just found it while trying to solve this issue as well.
Although the original question said that he has 7 tinymce's on the same page I think that my solution might work for him too but I do know it will work if there is one tinymce as was my case.
In my request spec I used this:
page.execute_script('$(tinymce.editors[0].setContent("my content here"))')
The page.execute_script
with tell it to run the jQuery function. It then finds the first tincymce editor and sets the content.
Worked like a charm for me. I think if there are more than one tinymce it can be called by its position.