public async Task RunAsync_StartsTask()
        {
            // arrange
            var func = A.Fake <Func <CancellationToken, Task> >();
            var sut  = new SingleProcess(func);

            // act
            await sut.RunAsync(CancellationToken.None);

            // assert
            A.CallTo(func).MustHaveHappenedOnceExactly();
        }