This tests that exceptions thrown by XHR.open() have reasonable messages.
On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
PASS xhrException.message is "Failed to execute 'open' on 'XMLHttpRequest': 'TRACE' HTTP method is unsupported."
PASS xhr.readyState is XMLHttpRequest.UNSENT
PASS xhr.open('GET', 'resources/xmlhttprequest-get-data.xml', true, badString, 'password'); threw exception Exception in toString().
PASS xhr.readyState is XMLHttpRequest.UNSENT
PASS xhr.open('GET', 'resources/xmlhttprequest-get-data.xml', true, 'username', badString); threw exception Exception in toString().
PASS xhr.readyState is XMLHttpRequest.UNSENT
PASS successfullyParsed is true
TEST COMPLETE