如何 运行 qunit assertions on resolving Promise

Question

我正在为 returns 承诺的函数编写测试，并且无法 运行 断言解决或拒绝承诺。我不能在这个项目上使用 ES6，所以我使用的是 rsvp.js 库，它声称实现了 Promises/A+ 规范。我使用的是最新的 qunit 版本 1.17.1

被测函数：

var loadGroups = function(data) {
     return new RSVP.Promise(function(resolve, reject) {
        var groups = [];
        // ... some code to populate the groups array
        if(groups.length > 0) {
            resolve(groups);
        } else {
            reject("No groups were loaded");
        }
    });
};

---

测试成功：

test('success test', function(assert) {
    assert.expect(1);

    var promise = loadGroups(testData);

    promise.then(function(groups) {
        assert.deepEquals(groups.length, 1);
    });

    return promise;
});

失败 "Expected 1 assertions, but 0 were run"

---

失败测试：

test('failure test', function(assert) {
    assert.expect(1);

    var promise = loadGroups([]);

    promise.then(null, function(message) {
        assert.equals(message, "No groups were loaded");
    });

    return promise;
});

失败 "Promise rejected during get promise when loading empty groups: No groups were loaded"

Answer 1

承诺通过链接工作。 Promises 是对值的不可变包装器。

当你这样做时：

promise.then(function(e){
   // do something
});

您没有更改 promise 您正在创建一个新的承诺。相反，您需要链接承诺：

test('success test', function(assert) {
    assert.expect(1);

    var promise = loadGroups(testData);

    // return the `then` and not the original promise.
    return promise.then(function(groups) {
        assert.deepEquals(groups.length, 1);
    });

});