Debugging

Sometimes when working with Marionette you’ll run into unexpected behaviour and need to do some debugging. This page outlines some of the Marionette methods that can be useful to you.

Please note that the best tools for debugging are the ones that ship with Gecko. This page doesn’t describe how to use those with Marionette. Also see a related topic about using the debugger with Marionette on MDN.

Seeing What’s on the Page

Sometimes it’s difficult to tell what is actually on the page that is being manipulated. Either because it happens too fast, the window isn’t big enough or you are manipulating a remote server! There are two methods that can help you out. The first is screenshot():

marionette.screenshot() # takes screenshot of entire frame
elem = marionette.find_element(By.ID, 'some-div')
marionette.screenshot(elem) # takes a screenshot of only the given element

Sometimes you just want to see the DOM layout. You can do this with the page_source property. Note that the page source depends on the context you are in:

print(marionette.page_source)
marionette.set_context('chrome')
print(marionette.page_source)