c# - mstest 如何创建对同一对象(累积)起作用的测试方法？

Question

我目前正在尝试对我正在构建的计算器(使用复合模式)进行测试。第一种方法应该添加 75 美元，效果很好，但是当第二种方法运行时，“服务”被重置并且有0 美元作为工作成本。如果我将这两种方法合二为一，那么一切都会按照我的预期进行。如何在服务领域保持值(value)？

[TestClass()]
public class JobTests
{
    private Service service;
    private LaborTime laborTime;
    private LaborRates laborRates;

    [TestInitialize]
    public void init()
    {
        service = new EmergencyService();
    }

    [TestMethod()]
    // add one hour of service at $75/50 rate
    public void Job_OnFullCost_Is75()
    {
        // Arrange
        laborTime = new LaborTime(
            checkIn: new DateTime(year: 2016, month: 7, day: 20, hour: 10, minute: 0, second: 0),
            checkOut: new DateTime(year: 2016, month: 7, day: 20, hour: 11, minute: 0, second: 0)
        );
        laborRates = new LaborRates(75, 50);
        service = new Labor(service, laborTime, laborRates);

        // Act
        var expected = 75.0M;
        var actual = service.JobCost;

        // Assert
        Assert.AreEqual(expected, actual);
    }

    [TestMethod()]
    // add another hour to the service, at same rate of $175/60
    public void Job_OnFullCost_Is125()
    {
        // Arrange
        laborTime = new LaborTime(
            checkIn: new DateTime(year: 2016, month: 7, day: 20, hour: 12, minute: 0, second: 0),
            checkOut: new DateTime(year: 2016, month: 7, day: 20, hour: 13, minute: 0, second: 0)
        );
        LaborRates laborRates = new LaborRates(75, 50);
        service = new Labor(service, laborTime, laborRates);
        //service.IsContinuation = true;

        // Act
        var expected = 125.0M;
        var actual = service.JobCost;

        // Assert
        Assert.AreEqual(expected, actual);
    }
}

Answer 1

由于不能保证所有单元测试都一起运行，或以特定顺序运行，因此最好避免在它们之间添加时间依赖(即要求它们在一个特定的顺序才能正常工作)。

相反，将添加人工的“困难部分”提取到单独的辅助方法中，并使您的两个方法测试特定场景。

[TestClass()]
public class JobTests
{
    private Service service;

    [TestInitialize]
    public void init()
    {
        service = new EmergencyService();
    }

    [TestMethod()]
    // add one hour of service at $75/50 rate
    public void Job_OnFullCost_Is75()
    {
        // Arrange
        AddHourOfService(75, 50);

        // Act
        var expected = 75.0M;
        var actual = service.JobCost;

        // Assert
        Assert.AreEqual(expected, actual);
    }

    [TestMethod()]
    // add another hour to the service, at same rate of $175/60
    public void Job_OnFullCost_Is125()
    {
        // Arrange
        AddHourOfService(75, 50);
        AddHourOfService(75, 50);

        // Act
        var expected = 125.0M;
        var actual = service.JobCost;

        // Assert
        Assert.AreEqual(expected, actual);
    }

    private void AddHourOfService(int cost, int time)
    {
        var laborTime = new LaborTime(
        checkIn: new DateTime(year: 2016, month: 7, day: 20, hour: 10, minute: 0, second: 0),
        checkOut: new DateTime(year: 2016, month: 7, day: 20, hour: 11, minute: 0, second: 0)
    );
        var laborRates = new LaborRates(75, 50);
        service = new Labor(service, laborTime, laborRates);
    }
}

除了消除测试之间的时间耦合之外，这还有一个很好的副作用，即使测试的目的直接从代码中显而易见。您不再需要像“以 75/50 美元的价格增加一小时的服务”这样的评论，因为 AddHourOfService(75, 50) 很明显会发生这种情况。让代码以这种方式 self 记录是件好事，因为注释很容易与您的代码不同步(正如您从第二条注释中看到的那样，上面写着“$175/60”，而这显然不是测试所做的)。