presentation-api/controlling-ua/startNewPresentation_unsettledpromise-manual.https.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Calling "start" when there is already an unsettled Promise returns a Promise rejected with an OperationError exception.</title>
<link rel="author" title="Tomoyuki Shimizu" href="https://github.com/tomoyukilabs/">
<link rel="help" href="http://w3c.github.io/presentation-api/#dfn-controlling-user-agent">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="common.js"></script>

<p>Click the button below to start the manual test. If prompted to select a device, please dismiss the dialog box. The test passes if a "PASS" result appears.</p>
<button id="presentBtn">Start Presentation Test</button>

<script>
    // disable the timeout function for the tests
    setup({explicit_timeout: true});

    // ----------
    // DOM Object
    // ----------
    var presentBtn = document.getElementById("presentBtn");

    // -----------------------------------------------
    // Terminate a presentation if started by accident
    // -----------------------------------------------
    function terminate(connection) {
        connection.terminate();
    }

    // -------------------------------------------
    // Start New Presentation Test (error) - begin
    // -------------------------------------------
    presentBtn.onclick = function () {
        presentBtn.disabled = true;
        promise_test(function (t) {
            var request1 = new PresentationRequest(presentationUrls),
                request2 = new PresentationRequest(presentationUrls);
            request1.start().then(terminate, function(){});
            return promise_rejects_dom(t, 'OperationError', request2.start().then(terminate));
        });
    };
    // -----------------------------------------
    // Start New Presentation Test (error) - end
    // -----------------------------------------
</script>