使用承諾的茉莉花異步測試

Question

我正在做一些使用角度承諾的茉莉花測試，並有一個與時間有關的問題。在這裏找到一個答案Unit-test promise-based code in Angular，但需要澄清這是如何工作的。鑑於then方法總是以異步方式處理，下面的測試如何保證通過。是否存在expect會在正在執行的then塊之前運行並且在值被分配之前運行期望的風險。或者...摘要循環保證在預期運行之前分配值。意思是說，摘要循環將有效地像阻塞調用一樣，保證在代碼被允許繼續之前所有的承諾都被解決。

function someService(){ 
    var deferred = $q.defer(); 
    deferred.resolve(myObj); 
    return deferred.promise; 
} 

it ('testing promise', function() { 
    var res; 
    var res2; 
    someService().then(function(obj){ 
    res = "test"; 
    }); 

    someService().then(function(obj){ 
    res2 = "test2"; 
    }); 

    $rootScope.$apply(); 
    expect(res).toBe('test'); 
    expect(res2).toBe('test2'); 
}); 

Answer 1

摘要週期將有效地表現得像一個阻塞調用，保證所允許的代碼之前進行的承諾都得到解決。

是的，雖然更確切地說，它可以保證已解決承諾的成功回調已經運行。

有一個非常相似example that shows how the digest cycle is tied to the success callbacks of promises in the docs for $q

Answer 2

雖然米哈爾的答案指向正確的想法，這裏的關鍵是，$apply()是呼籲相關範圍。以下是來自Angular文檔的示例：

it('should simulate promise', inject(function($q, $rootScope) { 
    var deferred = $q.defer(); 
    var promise = deferred.promise; 
    var resolvedValue; 

    promise.then(function(value) { resolvedValue = value; }); 
    expect(resolvedValue).toBeUndefined(); 

    // Simulate resolving of promise 
    deferred.resolve(123); 
    // Note that the 'then' function does not get called synchronously. 
    // This is because we want the promise API to always be async, whether or not 
    // it got called synchronously or asynchronously. 
    expect(resolvedValue).toBeUndefined(); 

    // Propagate promise resolution to 'then' functions using $apply(). 
    $rootScope.$apply(); 
    expect(resolvedValue).toEqual(123); 
}));