This test should trigger 'window.onerror' for the syntax error in the attribute handler, regardless of how it's set. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". window.onerror: "Uncaught SyntaxError: Failed to execute 'click' on 'HTMLElement': Unexpected token '%'" at window-onerror-11.html (Line: 11, Column: 25) Stack Trace: SyntaxError: Unexpected token '%' at window-onerror-11.html:31:24 Returning 'true': the error should not be reported in the console as an unhandled exception. window.onerror: "Uncaught SyntaxError: Failed to execute 'click' on 'HTMLElement': Unexpected token '%'" at window-onerror-11.html (Line: 33, Column: 34) Stack Trace: SyntaxError: Unexpected token '%' at window-onerror-11.html:31:24 Returning 'true': the error should not be reported in the console as an unhandled exception. window.onerror: "Uncaught SyntaxError: Failed to execute 'click' on 'HTMLElement': Unexpected token '%'" at window-onerror-11.html (Line: 33, Column: 52) Stack Trace: SyntaxError: Unexpected token '%' at window-onerror-11.html:31:24 Returning 'true': the error should not be reported in the console as an unhandled exception. PASS successfullyParsed is true TEST COMPLETE Button. Button 2 Button 3