gecko-dev/testing/web-platform/tests/custom-elements/CustomElementRegistry.html

<!DOCTYPE html>
<html>
<head>
<title>Custom Elements: CustomElementRegistry interface</title>
<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
<meta name="assert" content="CustomElementRegistry interface must exist">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
</head>
<body>
<div id="log"></div>
<script>

test(function () {
    assert_true('define' in CustomElementRegistry.prototype, '"define" exists on CustomElementRegistry.prototype');
    assert_true('define' in customElements, '"define" exists on window.customElements');
}, 'CustomElementRegistry interface must have define as a method');

test(function () {
    assert_throws({'name': 'TypeError'}, function () { customElements.define('badname', 1); },
        'customElements.define must throw a TypeError when the element interface is a number');
    assert_throws({'name': 'TypeError'}, function () { customElements.define('badname', '123'); },
        'customElements.define must throw a TypeError when the element interface is a string');
    assert_throws({'name': 'TypeError'}, function () { customElements.define('badname', {}); },
        'customElements.define must throw a TypeError when the element interface is an object');
    assert_throws({'name': 'TypeError'}, function () { customElements.define('badname', []); },
        'customElements.define must throw a TypeError when the element interface is an array');
}, 'customElements.define must throw when the element interface is not a constructor');

test(function () {
    customElements.define('custom-html-element', HTMLElement);
}, 'customElements.define must not throw the constructor is HTMLElement');

test(function () {
    class MyCustomElement extends HTMLElement {};

    assert_throws({'name': 'SyntaxError'}, function () { customElements.define(null, MyCustomElement); },
        'customElements.define must throw a SyntaxError if the tag name is null');
    assert_throws({'name': 'SyntaxError'}, function () { customElements.define('', MyCustomElement); },
        'customElements.define must throw a SyntaxError if the tag name is empty');
    assert_throws({'name': 'SyntaxError'}, function () { customElements.define('abc', MyCustomElement); },
        'customElements.define must throw a SyntaxError if the tag name does not contain "-"');
    assert_throws({'name': 'SyntaxError'}, function () { customElements.define('a-Bc', MyCustomElement); },
        'customElements.define must throw a SyntaxError if the tag name contains an upper case letter');

    var builtinTagNames = [
        'annotation-xml',
        'color-profile',
        'font-face',
        'font-face-src',
        'font-face-uri',
        'font-face-format',
        'font-face-name',
        'missing-glyph'
    ];

    for (var tagName of builtinTagNames) {
        assert_throws({'name': 'SyntaxError'}, function () { customElements.define(tagName, MyCustomElement); },
            'customElements.define must throw a SyntaxError if the tag name is "' + tagName + '"');
    }

}, 'customElements.define must throw with an invalid name');

test(function () {
    class SomeCustomElement extends HTMLElement {};

    var calls = [];
    var OtherCustomElement = new Proxy(class extends HTMLElement {}, {
        get: function (target, name) {
            calls.push(name);
            return target[name];
        }
    })

    customElements.define('some-custom-element', SomeCustomElement);
    assert_throws({'name': 'NotSupportedError'}, function () { customElements.define('some-custom-element', OtherCustomElement); },
        'customElements.define must throw a NotSupportedError if the specified tag name is already used');
    assert_array_equals(calls, [], 'customElements.define must validate the custom element name before getting the prototype of the constructor');

}, 'customElements.define must throw when there is already a custom element of the same name');

test(function () {
    class AnotherCustomElement extends HTMLElement {};

    customElements.define('another-custom-element', AnotherCustomElement);
    assert_throws({'name': 'NotSupportedError'}, function () { customElements.define('some-other-element', AnotherCustomElement); },
        'customElements.define must throw a NotSupportedError if the specified class already defines an element');

}, 'customElements.define must throw a NotSupportedError when there is already a custom element with the same class');

test(function () {
    var outerCalls = [];
    var OuterCustomElement = new Proxy(class extends HTMLElement { }, {
        get: function (target, name) {
            outerCalls.push(name);
            customElements.define('inner-custom-element', InnerCustomElement);
            return target[name];
        }
    });
    var innerCalls = [];
    var InnerCustomElement = new Proxy(class extends HTMLElement { }, {
        get: function (target, name) {
            outerCalls.push(name);
            return target[name];
        }
    });

    assert_throws({'name': 'NotSupportedError'}, function () { customElements.define('outer-custom-element', OuterCustomElement); },
        'customElements.define must throw a NotSupportedError if the specified class already defines an element');
    assert_array_equals(outerCalls, ['prototype'], 'customElements.define must get "prototype"');
    assert_array_equals(innerCalls, [],
        'customElements.define must throw a NotSupportedError when element definition is running flag is set'
        + ' before getting the prototype of the constructor');

}, 'customElements.define must throw a NotSupportedError when element definition is running flag is set');

test(function () {
    var calls = [];
    var ElementWithBadInnerConstructor = new Proxy(class extends HTMLElement { }, {
        get: function (target, name) {
            calls.push(name);
            customElements.define('inner-custom-element', 1);
            return target[name];
        }
    });

    assert_throws({'name': 'TypeError'}, function () {
        customElements.define('element-with-bad-inner-constructor', ElementWithBadInnerConstructor);
    }, 'customElements.define must throw a NotSupportedError if IsConstructor(constructor) is false');

    assert_array_equals(calls, ['prototype'], 'customElements.define must get "prototype"');
}, 'customElements.define must check IsConstructor on the constructor before checking the element definition is running flag');

test(function () {
    var calls = [];
    var ElementWithBadInnerName = new Proxy(class extends HTMLElement { }, {
        get: function (target, name) {
            calls.push(name);
            customElements.define('badname', class extends HTMLElement {});
            return target[name];
        }
    });

    assert_throws({'name': 'SyntaxError'}, function () {
        customElements.define('element-with-bad-inner-name', ElementWithBadInnerName);
    }, 'customElements.define must throw a SyntaxError if the specified name is not a valid custom element name');

    assert_array_equals(calls, ['prototype'], 'customElements.define must get "prototype"');
}, 'customElements.define must validate the custom element name before checking the element definition is running flag');

test(function () {
    var unresolvedElement = document.createElement('constructor-calls-define');
    document.body.appendChild(unresolvedElement);
    var elementUpgradedDuringUpgrade = document.createElement('defined-during-upgrade');
    document.body.appendChild(elementUpgradedDuringUpgrade);

    var DefinedDuringUpgrade = class extends HTMLElement { };

    class ConstructorCallsDefine extends HTMLElement {
        constructor() {
            customElements.define('defined-during-upgrade', DefinedDuringUpgrade);
            assert_false(unresolvedElement instanceof ConstructorCallsDefine);
            assert_true(elementUpgradedDuringUpgrade instanceof DefinedDuringUpgrade);
            super();
            assert_true(unresolvedElement instanceof ConstructorCallsDefine);
            assert_true(elementUpgradedDuringUpgrade instanceof DefinedDuringUpgrade);
        }
    }

    assert_false(unresolvedElement instanceof ConstructorCallsDefine);
    assert_false(elementUpgradedDuringUpgrade instanceof DefinedDuringUpgrade);

    customElements.define('constructor-calls-define', ConstructorCallsDefine);
}, 'customElements.define unset the element definition is running flag before upgrading custom elements');

(function () {
    var testCase = async_test('customElements.define must not throw'
        +' when defining another custom element in a different global object during Get(constructor, "prototype")', {timeout: 100});

    var iframe = document.createElement('iframe');
    iframe.onload = function () {
        testCase.step(function () {
            var InnerCustomElement = class extends iframe.contentWindow.HTMLElement {};
            var calls = [];
            var proxy = new Proxy(class extends HTMLElement { }, {
                get: function (target, name) {
                    calls.push(name);
                    iframe.contentWindow.customElements.define('another-custom-element', InnerCustomElement);
                    return target[name];
                }
            })
            customElements.define('element-with-inner-element-define', proxy);
            assert_array_equals(calls, ['prototype'], 'customElements.define must get "prototype"');
            assert_true(iframe.contentDocument.createElement('another-custom-element') instanceof InnerCustomElement);
        });
        document.body.removeChild(iframe);
        testCase.done();
    }

    document.body.appendChild(iframe);
})();

test(function () {
    var calls = [];
    var ElementWithBadInnerName = new Proxy(class extends HTMLElement { }, {
        get: function (target, name) {
            calls.push(name);
            customElements.define('badname', class extends HTMLElement {});
            return target[name];
        }
    });

    assert_throws({'name': 'SyntaxError'}, function () {
        customElements.define('element-with-bad-inner-name', ElementWithBadInnerName);
    }, 'customElements.define must throw a SyntaxError if the specified name is not a valid custom element name');

    assert_array_equals(calls, ['prototype'], 'customElements.define must get "prototype"');
}, '');

test(function () {
    var calls = [];
    var proxy = new Proxy(class extends HTMLElement { }, {
        get: function (target, name) {
            calls.push(name);
            return target[name];
        }
    });
    customElements.define('proxy-element', proxy);
    assert_array_equals(calls, ['prototype']);
}, 'customElements.define must get "prototype" property of the constructor');

test(function () {
    var proxy = new Proxy(class extends HTMLElement { }, {
        get: function (target, name) {
            throw {name: 'expectedError'};
        }
    });
    assert_throws({'name': 'expectedError'}, function () { customElements.define('element-with-string-prototype', proxy); });
}, 'customElements.define must rethrow an exception thrown while getting "prototype" property of the constructor');

test(function () {
    var returnedValue;
    var proxy = new Proxy(class extends HTMLElement { }, {
        get: function (target, name) { return returnedValue; }
    });

    returnedValue = null;
    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-string-prototype', proxy); },
        'customElements.define must throw when "prototype" property of the constructor is null');
    returnedValue = undefined;
    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-string-prototype', proxy); },
        'customElements.define must throw when "prototype" property of the constructor is undefined');
    returnedValue = 'hello';
    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-string-prototype', proxy); },
        'customElements.define must throw when "prototype" property of the constructor is a string');
    returnedValue = 1;
    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-string-prototype', proxy); },
        'customElements.define must throw when "prototype" property of the constructor is a number');

}, 'customElements.define must throw when "prototype" property of the constructor is not an object');

test(function () {
    var constructor = function () {}
    var calls = [];
    constructor.prototype = new Proxy(constructor.prototype, {
        get: function (target, name) {
            calls.push(name);
            return target[name];
        }
    });
    customElements.define('element-with-proxy-prototype', constructor);
    assert_array_equals(calls, ['connectedCallback', 'disconnectedCallback', 'adoptedCallback', 'attributeChangedCallback']);
}, 'customElements.define must get callbacks of the constructor prototype');

test(function () {
    var constructor = function () {}
    var calls = [];
    constructor.prototype = new Proxy(constructor.prototype, {
        get: function (target, name) {
            calls.push(name);
            if (name == 'disconnectedCallback')
                throw {name: 'expectedError'};
            return target[name];
        }
    });
    assert_throws({'name': 'expectedError'}, function () { customElements.define('element-with-throwing-callback', constructor); });
    assert_array_equals(calls, ['connectedCallback', 'disconnectedCallback'],
        'customElements.define must not get callbacks after one of the get throws');
}, 'customElements.define must rethrow an exception thrown while getting callbacks on the constructor prototype');

test(function () {
    var constructor = function () {}
    var calls = [];
    constructor.prototype = new Proxy(constructor.prototype, {
        get: function (target, name) {
            calls.push(name);
            if (name == 'adoptedCallback')
                return 1;
            return target[name];
        }
    });
    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-throwing-callback', constructor); });
    assert_array_equals(calls, ['connectedCallback', 'disconnectedCallback', 'adoptedCallback'],
        'customElements.define must not get callbacks after one of the conversion throws');
}, 'customElements.define must rethrow an exception thrown while converting a callback value to Function callback type');

test(function () {
    var constructor = function () {}
    constructor.prototype.attributeChangedCallback = function () { };
    var prototypeCalls = [];
    var callOrder = 0;
    constructor.prototype = new Proxy(constructor.prototype, {
        get: function (target, name) {
            if (name == 'prototype' || name == 'observedAttributes')
                throw 'Unexpected access to observedAttributes';
            prototypeCalls.push(callOrder++);
            prototypeCalls.push(name);
            return target[name];
        }
    });
    var constructorCalls = [];
    var proxy = new Proxy(constructor, {
        get: function (target, name) {
            constructorCalls.push(callOrder++);
            constructorCalls.push(name);
            return target[name];
        }
    });
    customElements.define('element-with-attribute-changed-callback', proxy);
    assert_array_equals(prototypeCalls, [1, 'connectedCallback', 2, 'disconnectedCallback', 3, 'adoptedCallback', 4, 'attributeChangedCallback']);
    assert_array_equals(constructorCalls, [0, 'prototype', 5, 'observedAttributes']);
}, 'customElements.define must get "observedAttributes" property on the constructor prototype when "attributeChangedCallback" is present');

test(function () {
    var constructor = function () {}
    constructor.prototype.attributeChangedCallback = function () { };
    var calls = [];
    var proxy = new Proxy(constructor, {
        get: function (target, name) {
            calls.push(name);
            if (name == 'observedAttributes')
                throw {name: 'expectedError'};
            return target[name];
        }
    });
    assert_throws({'name': 'expectedError'}, function () { customElements.define('element-with-throwing-observed-attributes', proxy); });
    assert_array_equals(calls, ['prototype', 'observedAttributes'],
        'customElements.define must get "prototype" and "observedAttributes" on the constructor');
}, 'customElements.define must rethrow an exception thrown while getting observedAttributes on the constructor prototype');

test(function () {
    var constructor = function () {}
    constructor.prototype.attributeChangedCallback = function () { };
    var calls = [];
    var proxy = new Proxy(constructor, {
        get: function (target, name) {
            calls.push(name);
            if (name == 'observedAttributes')
                return 1;
            return target[name];
        }
    });
    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-invalid-observed-attributes', proxy); });
    assert_array_equals(calls, ['prototype', 'observedAttributes'],
        'customElements.define must get "prototype" and "observedAttributes" on the constructor');
}, 'customElements.define must rethrow an exception thrown while converting the value of observedAttributes to sequence<DOMString>');

test(function () {
    var constructor = function () {}
    constructor.prototype.attributeChangedCallback = function () { };
    constructor.observedAttributes = {[Symbol.iterator]: function *() {
        yield 'foo';
        throw {name: 'SomeError'};
    }};
    assert_throws({'name': 'SomeError'}, function () { customElements.define('element-with-generator-observed-attributes', constructor); });
}, 'customElements.define must rethrow an exception thrown while iterating over observedAttributes to sequence<DOMString>');

test(function () {
    var constructor = function () {}
    constructor.prototype.attributeChangedCallback = function () { };
    constructor.observedAttributes = {[Symbol.iterator]: 1};
    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-observed-attributes-with-uncallable-iterator', constructor); });
}, 'customElements.define must rethrow an exception thrown while retrieving Symbol.iterator on observedAttributes');

test(function () {
    var constructor = function () {}
    constructor.observedAttributes = 1;
    customElements.define('element-without-callback-with-invalid-observed-attributes', constructor);
}, 'customElements.define must not throw even if "observedAttributes" fails to convert if "attributeChangedCallback" is not defined');

test(function () {
    class MyCustomElement extends HTMLElement {};
    customElements.define('my-custom-element', MyCustomElement);

    var instance = new MyCustomElement;
    assert_true(instance instanceof MyCustomElement,
        'An instance of a custom HTML element be an instance of the associated interface');

    assert_true(instance instanceof HTMLElement,
        'An instance of a custom HTML element must inherit from HTMLElement');

    assert_equals(instance.localName, 'my-custom-element',
        'An instance of a custom element must use the associated tag name');

    assert_equals(instance.namespaceURI, 'http://www.w3.org/1999/xhtml',
        'A custom element HTML must use HTML namespace');

}, 'customElements.define must define an instantiatable custom element');

test(function () {
    var disconnectedElement = document.createElement('some-custom');
    var connectedElementBeforeShadowHost = document.createElement('some-custom');
    var connectedElementAfterShadowHost = document.createElement('some-custom');
    var elementInShadowTree = document.createElement('some-custom');
    var childElementOfShadowHost = document.createElement('some-custom');
    var customShadowHost = document.createElement('some-custom');
    var elementInNestedShadowTree = document.createElement('some-custom');

    var container = document.createElement('div');
    var shadowHost = document.createElement('div');
    var shadowRoot = shadowHost.attachShadow({mode: 'closed'});
    container.appendChild(connectedElementBeforeShadowHost);
    container.appendChild(shadowHost);
    container.appendChild(connectedElementAfterShadowHost);
    shadowHost.appendChild(childElementOfShadowHost);
    shadowRoot.appendChild(elementInShadowTree);
    shadowRoot.appendChild(customShadowHost);

    var innerShadowRoot = customShadowHost.attachShadow({mode: 'closed'});
    innerShadowRoot.appendChild(elementInNestedShadowTree);

    var calls = [];
    class SomeCustomElement extends HTMLElement {
        constructor() {
            super();
            calls.push(this);
        }
    };

    document.body.appendChild(container);
    customElements.define('some-custom', SomeCustomElement);
    assert_array_equals(calls, [connectedElementBeforeShadowHost, elementInShadowTree, customShadowHost, elementInNestedShadowTree, childElementOfShadowHost, connectedElementAfterShadowHost]);
}, 'customElements.define must upgrade elements in the shadow-including tree order');

test(function () {
    assert_true('get' in CustomElementRegistry.prototype, '"get" exists on CustomElementRegistry.prototype');
    assert_true('get' in customElements, '"get" exists on window.customElements');
}, 'CustomElementRegistry interface must have get as a method');

test(function () {
    assert_equals(customElements.get('a-b'), undefined);
}, 'customElements.get must return undefined when the registry does not contain an entry with the given name');

test(function () {
    assert_equals(customElements.get('html'), undefined);
    assert_equals(customElements.get('span'), undefined);
    assert_equals(customElements.get('div'), undefined);
    assert_equals(customElements.get('g'), undefined);
    assert_equals(customElements.get('ab'), undefined);
}, 'customElements.get must return undefined when the registry does not contain an entry with the given name even if the name was not a valid custom element name');

test(function () {
    assert_equals(customElements.get('existing-custom-element'), undefined);
    class ExistingCustomElement extends HTMLElement {};
    customElements.define('existing-custom-element', ExistingCustomElement);
    assert_equals(customElements.get('existing-custom-element'), ExistingCustomElement);
}, 'customElements.get return the constructor of the entry with the given name when there is a matching entry.');

test(function () {
    assert_true(customElements.whenDefined('some-name') instanceof Promise);
}, 'customElements.whenDefined must return a promise for a valid custom element name');

test(function () {
    assert_equals(customElements.whenDefined('some-name'), customElements.whenDefined('some-name'));
}, 'customElements.whenDefined must return the same promise each time invoked for a valid custom element name which has not been defined');

promise_test(function () {
    var resolved = false;
    var rejected = false;
    customElements.whenDefined('a-b').then(function () { resolved = true; }, function () { rejected = true; });
    return Promise.resolve().then(function () {
        assert_false(resolved, 'The promise returned by "whenDefined" must not be resolved until a custom element is defined');
        assert_false(rejected, 'The promise returned by "whenDefined" must not be rejected until a custom element is defined');
    });
}, 'customElements.whenDefined must return an unresolved promise when the registry does not contain the entry with the given name')

promise_test(function () {
    var promise = customElements.whenDefined('badname');
    promise.then(function (value) { promise.resolved = value; }, function (value) { promise.rejected = value; });

    assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
    assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');

    return Promise.resolve().then(function () {
        assert_false('resolved' in promise, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
        assert_true('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
    });
}, 'customElements.whenDefined must return a rejected promise when the given name is not a valid custom element name');

promise_test(function () {
    customElements.define('preexisting-custom-element', class extends HTMLElement { });

    var promise = customElements.whenDefined('preexisting-custom-element');
    promise.then(function (value) { promise.resolved = value; }, function (value) { promise.rejected = value; });

    assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
    assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');

    return Promise.resolve().then(function () {
        assert_true('resolved' in promise, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
        assert_equals(promise.resolved, undefined,
            'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
        assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
    });
}, 'customElements.whenDefined must return a resolved promise when the registry contains the entry with the given name');

promise_test(function () {
    class AnotherExistingCustomElement extends HTMLElement {};
    customElements.define('another-existing-custom-element', AnotherExistingCustomElement);

    var promise1 = customElements.whenDefined('another-existing-custom-element');
    var promise2 = customElements.whenDefined('another-existing-custom-element');
    promise1.then(function (value) { promise1.resolved = value; }, function (value) { promise1.rejected = value; });
    promise2.then(function (value) { promise2.resolved = value; }, function (value) { promise2.rejected = value; });

    assert_not_equals(promise1, promise2);
    assert_false('resolved' in promise1, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
    assert_false('resolved' in promise2, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
    assert_false('rejected' in promise1, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
    assert_false('rejected' in promise2, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');

    return Promise.resolve().then(function () {
        assert_true('resolved' in promise1, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
        assert_equals(promise1.resolved, undefined, 'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
        assert_false('rejected' in promise1, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');

        assert_true('resolved' in promise2, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
        assert_equals(promise2.resolved, undefined, 'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
        assert_false('rejected' in promise2, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
    });
}, 'customElements.whenDefined must return a new resolved promise each time invoked when the registry contains the entry with the given name');

promise_test(function () {
    var promise = customElements.whenDefined('element-defined-after-whendefined');
    promise.then(function (value) { promise.resolved = value; }, function (value) { promise.rejected = value; });

    assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
    assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');

    var promiseAfterDefine;
    return Promise.resolve().then(function () {
        assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the element is defined');
        assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the element is defined');
        assert_equals(customElements.whenDefined('element-defined-after-whendefined'), promise,
            '"whenDefined" must return the same unresolved promise before the custom element is defined');
        customElements.define('element-defined-after-whendefined', class extends HTMLElement { });
        assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
        assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');

        promiseAfterDefine = customElements.whenDefined('element-defined-after-whendefined');
        promiseAfterDefine.then(function (value) { promiseAfterDefine.resolved = value; }, function (value) { promiseAfterDefine.rejected = value; });
        assert_not_equals(promiseAfterDefine, promise, '"whenDefined" must return a resolved promise once the custom element is defined');
        assert_false('resolved' in promiseAfterDefine, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
        assert_false('rejected' in promiseAfterDefine, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
    }).then(function () {
        assert_true('resolved' in promise, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
        assert_equals(promise.resolved, undefined,
            'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
        assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');

        assert_true('resolved' in promiseAfterDefine, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
        assert_equals(promiseAfterDefine.resolved, undefined,
            'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
        assert_false('rejected' in promiseAfterDefine, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
    });
}, 'A promise returned by customElements.whenDefined must be resolved by "define"');

</script>
</body>
</html>