{"id":56531,"date":"2012-12-10T07:55:24","date_gmt":"2012-12-10T15:55:24","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/devops\/?p=56531"},"modified":"2019-05-06T07:56:15","modified_gmt":"2019-05-06T15:56:15","slug":"asynchronous-calls-in-c-windows-store-unit-tests","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/devops\/asynchronous-calls-in-c-windows-store-unit-tests\/","title":{"rendered":"Asynchronous calls in C++ Windows Store Unit Tests"},"content":{"rendered":"

In Visual Studio 2012, we added support for the Async Test Methods in C#. You can call await <\/font><\/span>inside the test method body and the unit test framework will appropriately wait for its completion.<\/p>\n

Here is a sample test method.<\/p>\n

        <\/font><\/span>[<\/font><\/span>TestMethod<\/font><\/span><\/font>]<\/font><\/span><\/font><\/p>\n

        <\/font><\/span><\/span>public<\/font><\/span> <\/span>async<\/font><\/span> <\/span>Task<\/font><\/span><\/font> TestMethod1()<\/font><\/span><\/font><\/p>\n

        <\/font><\/span>{<\/font><\/font><\/span><\/p>\n

            <\/font><\/span><\/span>\/\/Arrange<\/font><\/span><\/font><\/span><\/p>\n

            <\/font><\/span><\/span>AtomPubClient<\/font><\/span> client = <\/span>new<\/font><\/span> <\/span>AtomPubClient<\/font><\/span><\/font>();<\/font><\/span><\/font><\/p>\n

            <\/font><\/span><\/span>Uri<\/font><\/span> uri = <\/span>new<\/font><\/span> <\/span>Uri<\/font><\/span>(<\/span>"http:\/\/blogs.msdn.com\/b\/mathew_aniyan\/atom.aspx"<\/font><\/span><\/font>);<\/font><\/span><\/font><\/p>\n

 <\/font><\/font><\/span><\/p>\n

            <\/font><\/span><\/span>\/\/Act<\/font><\/span><\/font><\/span><\/p>\n

            <\/font><\/span><\/span>var<\/font><\/span> result = <\/span>await<\/font><\/span><\/font> client.RetrieveFeedAsync(uri);<\/font><\/span><\/font><\/p>\n

 <\/font><\/font><\/span><\/p>\n

            <\/font><\/span><\/span>\/\/Assert<\/font><\/span><\/font><\/span><\/p>\n

            <\/font><\/span><\/span>Assert<\/font><\/span><\/font>.IsTrue(result.Items.Count > 0);<\/font><\/span><\/font><\/p>\n

        <\/font><\/span>}<\/font><\/font><\/span><\/span><\/p>\n

Notice how the method signature includes async<\/font><\/font><\/span> <\/span>Task<\/font><\/span><\/font> <\/font><\/span><\/font>and the method body contains a call to <\/font><\/font><\/span>await<\/font><\/span> client.RetrieveFeedAsync<\/span><\/font>.<\/font><\/span><\/font><\/p>\n

 <\/font><\/font><\/span><\/p>\n

If you are using C++ Windows Store Unit Tests, you cannot leverage this model since the language does not have equivalent constructs as the async-await pattern in C#. Asynchronous methods ,though, are ubiquitous in Windows Store applications. This blog will describe a model by which you can test asynchronous functions in a C++ Windows Store Unit Test.<\/p>\n

 <\/p>\n

To get started, open \u201cTools -> Extensions and Updates\u201d menu.<\/p>\n

\"image\"<\/a><\/p>\n

Search for and install C++ WinRT Async UnitTestLibrary.<\/p>\n

\"image\"<\/a><\/p>\n

This will install a new Project Template Unit Test Library with Async Helper (Windows Store apps)<\/b> under the Visual C++ -> Windows Store node in New Project dialog.<\/p>\n

\"image\"<\/a><\/p>\n

Go ahead and create a new Project with this template and then add the following code to the Test Method.<\/p>\n

              <\/font><\/span>TEST_METHOD(TestMethod1)<\/font><\/font><\/span><\/p>\n

              <\/font><\/span>{<\/font><\/font><\/span><\/p>\n

                     <\/font><\/span><\/span>\/\/Arrange<\/font><\/span><\/font><\/span><\/p>\n

                     <\/font><\/span>Uri^ uri = <\/font><\/span>ref<\/font><\/span> <\/span>new<\/font><\/span> Uri(<\/span>"http:\/\/blogs.msdn.com\/b\/mathew_aniyan\/atom.aspx"<\/font><\/span><\/font>);<\/font><\/span><\/font><\/p>\n

                     <\/font><\/span>AtomPubClient^ client = <\/font><\/span>ref<\/font><\/span> <\/span>new<\/font><\/span><\/font> AtomPubClient();<\/font><\/span><\/font><\/p>\n

                     <\/font><\/span><\/span>auto<\/font><\/span> count = std::make_shared<<\/span>int<\/font><\/span><\/font>>(0);<\/font><\/span><\/font><\/p>\n

 <\/font><\/font><\/span><\/p>\n

                     <\/font><\/span><\/span>\/\/Act<\/font><\/span><\/font><\/span><\/p>\n

                     <\/font><\/span>AsyncHelper::RunSynced(task<SyndicationFeed^>(client->RetrieveFeedAsync(uri)).then([count] (SyndicationFeed^ feed)<\/font><\/font><\/span><\/p>\n

                     <\/font><\/span>{<\/font><\/font><\/span><\/p>\n

                           <\/font><\/span>*count = feed->Items->Size;<\/font><\/font><\/span><\/p>\n

                     <\/font><\/span>}));<\/font><\/font><\/span><\/p>\n

 <\/font><\/font><\/span><\/p>\n

                     <\/font><\/span><\/span>\/\/Assert<\/font><\/span><\/font><\/span><\/p>\n

                     <\/font><\/span>Assert::IsTrue(*count > 0);<\/font><\/font><\/span><\/p>\n

              <\/font><\/span>}<\/font><\/font><\/span><\/span><\/p>\n

 <\/font><\/font><\/span><\/p>\n

Notice how AsyncHelper::RunSynced<\/span> <\/font><\/font><\/span><\/font>method is used. This will ensure that the task argument is completed before proceeding with the test method.<\/p>\n

 <\/font><\/font><\/span><\/p>\n

If you open asynchelper.h file in the solution, you can see how RunSynced is implemented. The key code snippet is<\/p>\n

\/\/ Spin wait and exercise message pump<\/font><\/font><\/span><\/span><\/p>\n

                     <\/font><\/span>DWORD waitResult = STATUS_PENDING;<\/font><\/font><\/span><\/p>\n

                     <\/font><\/span><\/span>while<\/font><\/span><\/font>(waitResult != WAIT_OBJECT_0)<\/font><\/span><\/font><\/p>\n

                     <\/font><\/span>{<\/font><\/font><\/span><\/p>\n

                           <\/font><\/span>dispatcher->ProcessEvents(Windows::UI::Core::CoreProcessEventsOption::ProcessAllIfPresent);<\/font><\/font><\/span><\/p>\n

                           <\/font><\/span>waitResult = WaitForSingleObjectEx(hEvent, 0, <\/font><\/span>true<\/font><\/span><\/font>);<\/font><\/span><\/font><\/p>\n

                     <\/font><\/span>}<\/font><\/font><\/span><\/span><\/p>\n

You can now go ahead and run this test. You will see that the test passes.<\/p>\n

 <\/font><\/font><\/span><\/p>\n

This solution approach was identified by the Patterns  <\/span>& Practices team and used in their Hilo project.<\/font><\/a><\/p>\n

Direct link to the project template in Visual Studio Gallery – http:\/\/visualstudiogallery.msdn.microsoft.com\/744fb771-756e-4801-811d-8994d82466dd<\/font><\/a><\/p>\n

The project template is published to codeplex at http:\/\/asynccppunittestlib.codeplex.com\/<\/font><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

In Visual Studio 2012, we added support for the Async Test Methods in C#. You can call await inside the test method body and the unit test framework will appropriately wait for its completion. Here is a sample test method.         [TestMethod]         public async Task TestMethod1()         {             \/\/Arrange             AtomPubClient client = […]<\/p>\n","protected":false},"author":241,"featured_media":45953,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-56531","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-devops"],"acf":[],"blog_post_summary":"

In Visual Studio 2012, we added support for the Async Test Methods in C#. You can call await inside the test method body and the unit test framework will appropriately wait for its completion. Here is a sample test method.         [TestMethod]         public async Task TestMethod1()         {             \/\/Arrange             AtomPubClient client = […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/posts\/56531","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/users\/241"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/comments?post=56531"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/posts\/56531\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/media\/45953"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/media?parent=56531"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/categories?post=56531"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/devops\/wp-json\/wp\/v2\/tags?post=56531"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}