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POHow to Unit Test DelegateCommand that calls async methods in MVVM
 

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    <p>I am new to Unit Testing MVVM and using PRISM on my project. I am implementing Unit Testing on our current project and not having luck finding resources online that would tell me how totest DelegateCommand that calls async method. This is a follow up question to my post - <a href="https://stackoverflow.com/questions/15631635/how-to-unit-test-a-viewmodel-with-async-method">How to Unit Test a ViewModel with async method.</a> on how to unit test an async methods in MVVM and was answered that public methods can be tested using async TestMethod. This scenario will work only if the method that I want to test are public methods.</p> <p>The problem is I want to test my DelegateCommand as this are the only public details that I want to expose on other classes and everything else are private. I can expose my private methods as public but I will never do this as its a bad design. I am not sure on how to go about this - Is DelegateCommand needs to be tested, or there are some other work around this? I am interested to know how other go about this and somehow lead me to the right path.</p> <p>Here are my codes again </p> <pre><code> async void GetTasksAsync() { this.SimpleTasks.Clear(); Func&lt;IList&lt;ISimpleTask&gt;&gt; taskAction = () =&gt; { var result = this.dataService.GetTasks(); if (token.IsCancellationRequested) return null; return result; }; IsBusyTreeView = true; Task&lt;IList&lt;ISimpleTask&gt;&gt; getTasksTask = Task&lt;IList&lt;ISimpleTask&gt;&gt;.Factory.StartNew(taskAction, token); var l = await getTasksTask; // waits for getTasksTask if (l != null) { foreach (ISimpleTask t in l) { this.SimpleTasks.Add(t); // adds to ViewModel.SimpleTask } } } </code></pre> <p>also here is the command in my VM that calls the async method above</p> <pre><code> this.GetTasksCommand = new DelegateCommand(this.GetTasks); void GetTasks() { GetTasksAsync(); } </code></pre> <p>and now my Test Method goes like </p> <pre><code> [TestMethod] public void Command_Test_GetTasksCommand() { MyViewModel.GetTaskCommand.Execute(); // this should populate ViewModel.SimpleTask Assert.IsTrue(MyBiewModel.SimpleTask != null) } </code></pre> <p>Currently what I am getting is that my ViewModel.SimpleTask = null this is because it does not wait for the async method to finish.</p>
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