Simulate a delay in execution in Unit Test using Moq

When you setup your mock you can tell the thread to sleep in the return func:

Mock<IMyService> myService = new Mock<IMyService>();

myService.Setup(x => x.GetResultDelayed()).Returns(() => {
    Thread.Sleep(100);
    return "result";
});

If running asynchronous code, Moq has the ability to delay the response with the second parameter via a TimeSpan

mockFooService
    .Setup(m => m.GetFooAsync())
    .ReturnsAsync(new Foo(), TimeSpan.FromMilliseconds(500)); // Delay return for 500 milliseconds.

If you need to specify a different delay each time the method is called, you can use .SetupSequence like

mockFooService
    .SetupSequence(m => m.GetFooAsync())
    .Returns(new Foo())
    .Returns(Task.Run(async () => 
    {
        await Task.Delay(500) // Delay return for 500 milliseconds.
        return new Foo();
    })

If you want a Moq mock to just sit and do nothing for a while you can use a callback:

Mock<IFoo> mockFoo = new Mock<IFoo>();
mockFoo.Setup(f => f.Bar())
       .Callback(() => Thread.Sleep(1000))
       .Returns("test");

string result = mockFoo.Object.Bar(); // will take 1 second to return

Assert.AreEqual("test", result);

I've tried that in LinqPad and if you adjust the Thread.Sleep() the execution time varies accordingly.