Mozmill tests frequently use controller.waitForPageLoad to ensure that a page loads completely before further testing. Marionette.navigate() includes an equivalent check, but other ways that we load a new page using Marionette, including after element.click(), do not. It would be helpful to include a standard method for making the equivalent of mozmill's waitForPageLoad check in the Firefox UI Test libraries.
To accurately being able to catch a page load we would have to wait for events, or if possible we could check if the former DOM element gets stale. That means we have to save the state before, trigger the action, and wait for the expected stale status or event (unload and load). I would suggest we try with stale elements first. If that doesn't work we would need event listeners.
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