Non-determinism in tests

1.cs

public class SomeService
{
    public void FirePeriodicJob()
    {
        /* Runs asynchronously */
    }
}

2.cs

[Fact]
public void Test()
{
    var sut = new SomeService();

    sut.FirePeriodicJob();

    // Give the job time to complete
    Thread.Sleep(10000);

    /* Verify the effects of the job */
}

3.cs

[Fact]
public void Test()
{
    var sut = new SomeService();

    sut.FirePeriodicJob();

    // Give the job time to complete
    Task.Delay(10000).Wait();

    /* Verify the effects of the job */
}

4.cs

[Fact]
public void Test()
{
    var sut = new CustomerService();

    Customer customer = sut.Create("Name");

    Assert.Equal(DateTime.Now, customer.DateCreated);
}

5.cs

[Fact]
public void Test()
{
    DateTime now = DateTime.Now;
    var sut = new CustomerService();

    Customer customer = sut.Create("Name", now);

    Assert.Equal(now, customer.DateCreated);
}

6.cs

public static class SystemDateTime
{
    private static Func<DateTime> _func;
 
    public static DateTime Now
    {
        get { return _func(); }
    }
 
    public static void Init(Func<DateTime> func)
    {
        _func = func;
    }
}

7.cs

// Initialization code for production
SystemDateTime.Init(() => DateTime.UtcNow);

8.cs

// Initialization code for unit tests
SystemDateTime.Init(() => new DateTime(2016, 10, 3));