Unit Test Method That Calls Async Method

Asked Mar 02 '17 at 15:05

Active Mar 02 '17 at 15:34

Viewed 358 times

I have code like this

public void Foo(...) 
{ 
   ...
   FooAsync(...);
   ...
}

private async void FooAsync(...)
{
   await Task.Run(() => Process(...));
}

private void Process(...)
{
   // slow process
}

I want to unit test Foo, and one of the things I want to test is that some method is called on some object (that I have access to) within the Process method. The problem is that the Process method gets called after the check is made in the unit test. How do I test this so that it behaves more synchronously?

edited Mar 02 '17 at 15:07

asked Mar 02 '17 at 15:05

Sachin Kainth

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Which testing framework are you using? – Connell.O'Donnell Mar 02 '17 at 15:06
4

For starters, you should change the return type of FooAsync to Task. Try to avoid using async void https://msdn.microsoft.com/en-us/magazine/jj991977.aspx – Connell.O'Donnell Mar 02 '17 at 15:08
@Connell.O'Donnell Nunit – Sachin Kainth Mar 02 '17 at 15:09
2

Provide a [mcve] that can be used to reproduce the problem. Also show what you have tried so far and identify the current and desired behavior – Nkosi Mar 02 '17 at 15:09
@Connell.O'Donnell ok – Sachin Kainth Mar 02 '17 at 15:10
Possible duplicate of [How do I test an async method with NUnit, eventually with another framework?](http://stackoverflow.com/questions/12191831/how-do-i-test-an-async-method-with-nunit-eventually-with-another-framework) – Igor Mar 02 '17 at 15:10
@SachinKainth as an aside. From a design perspective, Foo is a misleading method. It is declared as a synchronous method that deceives you by calling an async method. – Nkosi Mar 02 '17 at 15:13
@Nkosi I cannot change the signature of Foo. – Sachin Kainth Mar 02 '17 at 15:13
@SachinKainth, can you change the signature of any of those methods? – Nkosi Mar 02 '17 at 15:14
@Nkosi Yes, all except Foo. – Sachin Kainth Mar 02 '17 at 15:14
@SachinKainth then abstract the `FooAsync` out into a dependency that properly implements the async members and unit test the implementation of extracted functionality. Make FooAsyn and Process proper async methods – Nkosi Mar 02 '17 at 15:16
4

`I cannot change the signature of Foo` - well, that's a problem, because `Foo` is where the problem is. – Stephen Cleary Mar 02 '17 at 15:43

Unit Test Method That Calls Async Method

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