取消一个纯ECMAScript 6 Promise链。

有没有一种方法可以清除JavaScript Promise实例的 .then 方法？

我在QUnit之上编写了一个JavaScript测试框架。该框架通过在Promise中运行每个测试来同步运行它们。（对于这段代码块的长度，我很抱歉。我尽力进行了注释，所以感觉不那么乏味。）

/* Promise extension -- used for easily making an async step with a
       timeout without the Promise knowing anything about the function 
       it's waiting on */
$$.extend(Promise, {
    asyncTimeout: function (timeToLive, errorMessage) {
        var error = new Error(errorMessage || "Operation timed out.");
        var res, // resolve()
            rej, // reject()
            t,   // timeout instance
            rst, // reset timeout function
            p,   // the promise instance
            at;  // the returned asyncTimeout instance

        function createTimeout(reject, tempTtl) {
            return setTimeout(function () {
                // triggers a timeout event on the asyncTimeout object so that,
                // if we want, we can do stuff outside of a .catch() block
                // (may not be needed?)
                $$(at).trigger("timeout");

                reject(error);
            }, tempTtl || timeToLive);
        }

        p = new Promise(function (resolve, reject) {
            if (timeToLive != -1) {
                t = createTimeout(reject);

                // reset function -- allows a one-time timeout different
                //    from the one original specified
                rst = function (tempTtl) {
                    clearTimeout(t);
                    t = createTimeout(reject, tempTtl);
                }
            } else {
                // timeToLive = -1 -- allow this promise to run indefinitely
                // used while debugging
                t = 0;
                rst = function () { return; };
            }

            res = function () {
                clearTimeout(t);
                resolve();
            };

            rej = reject;
        });

        return at = {
            promise: p,
            resolve: res,
            reject: rej,
            reset: rst,
            timeout: t
        };
    }
});

/* framework module members... */

test: function (name, fn, options) {
    var mod = this; // local reference to framework module since promises
                    // run code under the window object

    var defaultOptions = {
        // default max running time is 5 seconds
        timeout: 5000
    }

    options = $$.extend({}, defaultOptions, options);

    // remove timeout when debugging is enabled
    options.timeout = mod.debugging ? -1 : options.timeout;

    // call to QUnit.test()
    test(name, function (assert) {
        // tell QUnit this is an async test so it doesn't run other tests
        // until done() is called
        var done = assert.async();
        return new Promise(function (resolve, reject) {
            console.log("Beginning: " + name);

            var at = Promise.asyncTimeout(options.timeout, "Test timed out.");
            $$(at).one("timeout", function () {
                // assert.fail() is just an extension I made that literally calls
                // assert.ok(false, msg);
                assert.fail("Test timed out");
            });

            // run test function
            var result = fn.call(mod, assert, at.reset);

            // if the test returns a Promise, resolve it before resolving the test promise
            if (result && result.constructor === Promise) {
                // catch unhandled errors thrown by the test so future tests will run
                result.catch(function (error) {
                    var msg = "Unhandled error occurred."
                    if (error) {
                        msg = error.message + "\n" + error.stack;
                    }

                    assert.fail(msg);
                }).then(function () {
                    // resolve the timeout Promise
                    at.resolve();
                    resolve();
                });
            } else {
                // if test does not return a Promise, simply clear the timeout
                // and resolve our test Promise
                at.resolve();
                resolve();
            }
        }).then(function () {
            // tell QUnit that the test is over so that it can clean up and start the next test
            done();
            console.log("Ending: " + name);
        });
    });
}

如果测试超时，我的超时Promise将在测试上assert.fail()，以便将测试标记为失败，这很好，但测试继续运行，因为测试Promise (result) 仍在等待解决它。
我需要一个良好的方法来取消我的测试。我可以通过在框架模块this.cancelTest上创建一个字段或类似的东西，并且每隔一段时间（例如在每个then()迭代的开始）在测试中检查是否要取消来完成它。然而，理想情况下，我可以使用$$(at).on("timeout", /* something here */)来清除剩余的result变量上的所有then()，以便不运行测试的其余部分。
有像这样的东西存在吗？
快速更新
我尝试使用Promise.race([result, at.promise])。 它没有起作用。
更新2 + 混淆
为了解除阻塞，我添加了一些具有mod.cancelTest/轮询测试思路的行。 （我还删除了事件触发器。）

return new Promise(function (resolve, reject) {
    console.log("Beginning: " + name);

    var at = Promise.asyncTimeout(options.timeout, "Test timed out.");
    at.promise.catch(function () {
        // end the test if it times out
        mod.cancelTest = true;
        assert.fail("Test timed out");
        resolve();
    });

    // ...
    
}).then(function () {
    // tell QUnit that the test is over so that it can clean up and start the next test
    done();
    console.log("Ending: " + name);
});

我在catch语句中设置了断点，并且它被命中了。现在让我感到困惑的是then()语句没有被调用。有什么想法吗？

更新 3

我解决了最后一个问题。fn.call()抛出了一个错误，我没有捕获到，因此测试 Promise 在at.promise.catch()处理之前就被拒绝了。