Verify basic support for DOM event listener registration. The root svg element has an onload handler where a click event listener is registered on group element 'Start Button'.
If UI events listener registration is supported (and UI events), when the user clicks on the button a text node is inserted reading "Event Listeners supported".
At the end of the test, the start test button is changed to green, and the click event listener is removed from the the start button.
Subsequent clicks on the start button should cause no effect if the event listener has been removed successfully. If additional lines of text appear in the document that say "Event Listeners supported", then the implementation has not successfully removed the event listener.
This test requires user interaction. Run the test, then click on the grey rectangle. If it turns green, click it again.
After clicking once on the button, the rectangle should have a green fill and the text "Event listeners supported" should appear, once.