Unit testing with Mocks when SUT is leveraging Task Parallel Libaray
- by StevenH
I am trying to unit test / verify that a method is being called on a dependency, by the system under test.
The depenedency is IFoo.
The dependent class is IBar.
IBar is implemented as Bar.
Bar will call Start() on IFoo in a new (System.Threading.Tasks.)Task, when Start() is called on Bar instance.
Unit Test (Moq):
[Test]
public void StartBar_ShouldCallStartOnAllFoo_WhenFoosExist()
{
//ARRANGE
//Create a foo, and setup expectation
var mockFoo0 = new Mock<IFoo>();
mockFoo0.Setup(foo => foo.Start());
var mockFoo1 = new Mock<IFoo>();
mockFoo1.Setup(foo => foo.Start());
//Add mockobjects to a collection
var foos = new List<IFoo>
{
mockFoo0.Object,
mockFoo1.Object
};
IBar sutBar = new Bar(foos);
//ACT
sutBar.Start(); //Should call mockFoo.Start()
//ASSERT
mockFoo0.VerifyAll();
mockFoo1.VerifyAll();
}
Implementation of IBar as Bar:
class Bar : IBar
{
private IEnumerable<IFoo> Foos { get; set; }
public Bar(IEnumerable<IFoo> foos)
{
Foos = foos;
}
public void Start()
{
foreach(var foo in Foos)
{
Task.Factory.StartNew(
() =>
{
foo.Start();
});
}
}
}
I appears that the issue is obviously due to the fact that the call to "foo.Start()" is taking place on another thread (/task), and the mock (Moq framework) can't detect it. But I could be wrong.
Thanks
