Unit Testing, Part II, Synchronisation Issues

ComplexBusinessOperations-1.cs

public class ComplexBusinessOperations
{
    private int moneyEarnedSoFar;

    public int MoneyEarnedSoFar
    {
        get { return moneyEarnedSoFar; }
    }

    public void EarnMoney(int investment)
    {
        EarnMoneySubTaks(investment);
        EarnMoneySubTaks(investment);
    }

    private void EarnMoneySubTaks(int investment)
    {
        for (int i = 0; i < investment; i++)
        {
            var result = EarnOneDollar();
            moneyEarnedSoFar += result;
        }
    }

    private int EarnOneDollar()
    {
        // This operation takes a while
        Thread.Sleep(50);
        return 1;
    }
}

ComplexBusinessOperations-2.cs

public class ComplexBusinessOperations
{
    private int moneyEarnedSoFar;

    public int MoneyEarnedSoFar
    {
        get { return moneyEarnedSoFar; }
    }

    public async Task EarnMoneyAsync(int investment)
    {
        var firstMoneyEarner = EarnMoneySubTaskAsync(investment);
        var secondMoneyEarner = EarnMoneySubTaskAsync(investment);
        await TaskEx.WhenAll(firstMoneyEarner, secondMoneyEarner);
    }

    private async Task EarnMoneySubTaskAsync(int investment)
    {
        for (int i = 0; i < investment; i++)
        {
            var result = await EarnOneDollarAsync();
            moneyEarnedSoFar += result;
        }
    }

    private Task<int> EarnOneDollarAsync()
    {
        return TaskEx.Run(
            () =>
                {
                    // This operation takes a while
                    Thread.Sleep(50);
                    return 1;
                });
    }
}

ComplexBusinessOperationsTest-1.cs

[Test]
public void EarnMoney()
{
    var toTest = new ComplexBusinessOperations();
    toTest.EarnMoney(200);
    Assert.AreEqual(400, toTest.MoneyEarnedSoFar);
}

ComplexBusinessOperationsTest-2.cs

[Test]
public void EarnMoney()
{
    var toTest = new ComplexBusinessOperations();
    var task = toTest.EarnMoneyAsync(200);
    task.Wait();
    Assert.AreEqual(400, toTest.MoneyEarnedSoFar);
}