Checks that an exception is thrown when a dictionary value cannot be converted to a String On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS new MessageEvent('message', {origin: 'test'}).origin is "test" PASS new MessageEvent('message', {origin: 2}).origin is "2" PASS new MessageEvent('message', {origin: nonConvertibleToString}) threw exception Exception in toString(). PASS successfullyParsed is true TEST COMPLETE