How can I tell Moq to return a Task

Question

I ve got an interface which declares  Task DoSomethingAsync      I m using MoqFramework for my tests    TestMethod    public async Task MyAsyncTest        Mock lt ISomeInterface gt  mock   new Mock lt ISomeInterface gt        mock Setup arg   gt  arg DoSomethingAsync    Callback      gt     lt my code here gt                 Then in my test I execute the code which invokes await DoSomethingAsync    And the test just fails on that line  What am I doing wrong

User · Accepted Answer

Your method doesn t have any callbacks so there is no reason to use  CallBack    You can simply return a Task with the desired values using  Returns   and Task FromResult  e g    MyType someValue      mock Setup arg  gt arg DoSomethingAsync                 Returns Task FromResult someValue      Update 2014-06-22  Moq 4 2 has two new extension methods to assist with this   mock Setup arg  gt arg DoSomethingAsync         ReturnsAsync someValue    mock Setup arg  gt arg DoSomethingAsync                 ThrowsAsync new InvalidOperationException       Update 2016-05-05   As Seth Flowers mentions in the other answer  ReturnsAsync is only available for methods that return a Task lt T gt   For methods that return only a Task     Returns Task FromResult default object      can be used   As shown in this answer  in  NET 4 6 this is simplified to  Returns Task CompletedTask    e g    mock Setup arg  gt arg DoSomethingAsync                 Returns Task CompletedTask

User · Answer

Similar Issue  I have an interface that looked roughly like   Task DoSomething int arg     Symptoms  My unit test failed when my service under test awaited the call to DoSomething    Fix  Unlike the accepted answer  you are unable to call  ReturnsAsync   on your Setup   of this method in this scenario  because the method returns the non-generic Task  rather than Task lt T gt     However  you are still able to use  Returns Task FromResult default object    on the setup  allowing the test to pass

User · Answer

You only need to add  Returns Task FromResult 0    after the Callback   Example   mock Setup arg   gt  arg DoSomethingAsync         Callback      gt     lt my code here gt          Returns Task FromResult 0

User · Answer

Now you can also use Talentsoft Moq SetupAsync package https   github com TalentSoft Moq SetupAsync  Which on the base on the answers found here and ideas proposed to Moq but still not yet implemented here  https   github com moq moq4 issues 384  greatly simplify setup of async methods  Few examples found in previous responses done with SetupAsync extension   mock SetupAsync arg  gt arg DoSomethingAsync     mock SetupAsync arg  gt arg DoSomethingAsync    Callback      gt     lt my code here gt      mock SetupAsync arg  gt arg DoSomethingAsync    Throws new InvalidOperationException

[c#] How can I tell Moq to return a Task?

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