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，"service"被重置并且作业成本为 0 美元。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。如何在服务领域保值？

[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 /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 5/60
    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

由于不能保证单元测试全部运行在一起，或者按特定顺序运行，最好避免添加 时间依赖性 在它们之间（即要求它们按特定顺序运行才能正常工作）。

相反，将增加劳动力的 "hard parts" 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 /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 5/60
    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 "add one hour of service at /50 rate" 这样的注释，因为 AddHourOfService(75, 50) 很明显会发生这种情况。让代码以这种方式自我记录是件好事，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）。

mstest 如何创建对同一对象（累积）起作用的测试方法？

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