测试在循环中执行的代码

Question

我以为我会尝试在命令行上模拟ATM机的代码kata.我决定使用TDD来推动设计.我遇到了一个有趣的场景,我很好奇其他人在这个场景中所做的事情.

如果你在我的AtmMachine课上看(在底部),你会注意到我正在故意退出我的while循环,这样我的测试就不会超时.这对我来说就像一个代码味道,我想知道其他人是否做过这样的事情.

我目前的感受是分开的:

1. 通过尝试对持续执行进行单元测试,"我做错了"
2. 无法为它编写单元测试意味着"while"是错误的构造

以下是迄今为止我为atm机器进行的单元测试:

[TestClass]
public class when_atm_starts
{
    private static readonly string WELCOME_MSG = "Welcome to Al Banco de Ruiz!";

    private AtmMachine _atm;
    private Mock<IAtmInput> _inputMock;
    private Mock<IAtmOutput> _outputMock;
    private Mock<ILogger> _loggerMock;
    private Mock<ICommandFactory> _cmdFactoryMock;


    [TestInitialize]
    public void BeforeEachTest()
    {
        _inputMock = new Mock<IAtmInput>();
        _outputMock = new Mock<IAtmOutput>();
        _loggerMock = new Mock<ILogger>();
        _cmdFactoryMock = new Mock<ICommandFactory>();

        _atm = new AtmMachine(_inputMock.Object, _outputMock.Object, _loggerMock.Object, _cmdFactoryMock.Object);
    }


    [TestMethod]
    public void no_one_should_be_logged_in()
    {
        this.SetupForCancelledUser();

        _atm.Start();

        Assert.IsNull(_atm.CurrentUser);
    }

    [TestMethod]
    public void should_print_welcome_to_output()
    {
        this.SetupForCancelledUser();

        _atm.Start();

        _outputMock.Verify(o => o.Write(WELCOME_MSG));
    }

    [TestMethod]
    public void should_execute_login_command()
    {
        Mock<ILoginCommand> loginCmdMock = new Mock<ILoginCommand>();

        _cmdFactoryMock.Setup(cf => cf.GetLoginCommand(_inputMock.Object, _outputMock.Object))
            .Returns(loginCmdMock.Object);

        loginCmdMock.Setup(lc => lc.LogonUser())
            .Returns(AtmUser.CancelledUser);

        _atm.Start();

        loginCmdMock.Verify(lc => lc.LogonUser());
    }


    private void SetupForCancelledUser()
    {
        Mock<ILoginCommand> loginCmdMock = new Mock<ILoginCommand>();

        _cmdFactoryMock.Setup(cf => cf.GetLoginCommand(_inputMock.Object, _outputMock.Object))
            .Returns(loginCmdMock.Object);

        loginCmdMock.Setup(lc => lc.LogonUser())
            .Returns(AtmUser.CancelledUser);
    }
}

这是相应的AtmMachine类.

public class AtmMachine
{
    public static readonly string WELCOME_MSG = "Welcome to Al Banco de Ruiz!";


    private bool _shouldContinue;
    private ILogger _log;
    private ICommandFactory _cmdFactory;
    private IAtmInput _input;
    private IAtmOutput _output;


    public object CurrentUser { get; set; }


    public AtmMachine(
        IAtmInput input,
        IAtmOutput output,
        ILogger logger,
        ICommandFactory cmdFactory)
    {
        this._input = input;
        this._output = output;
        this._log = logger;
        this._cmdFactory = cmdFactory;
    }


    public void Start()
    {
        _shouldContinue = true;

        while (_shouldContinue)
        {
            _output.Clear();
            _output.Write(WELCOME_MSG);
            AtmUser user = this.GetNextUser();

            if (user == AtmUser.CancelledUser) { _shouldContinue = false; }

            _shouldContinue = false;
        }
    }


    private AtmUser GetNextUser()
    {
        ILoginCommand loginCmd = _cmdFactory.GetLoginCommand(_input, _output);
        return loginCmd.LogonUser();
    }
}

Answer 1

你以这种方式测试循环是正确的.除了"没有人登录"之外,我没有太多关于你试图试驾的功能的背景,所以我会对我的建议采取一些自由.

首先,对于循环测试,您可以通过几种方式执行此操作,具体取决于您的偏好.第一种方法是将循环条件提取到一个方法中,该方法可以在用于测试的子类中重写.

// In your AtmMachine
public void Start()
{
    _shouldContinue = true;

    while (stillRunning())
    {
        // Do some ATM type stuff
    }
}

protected virtual bool stillRunning() {
    return _shouldContinue;
}

在测试中,您可以创建一个覆盖的特殊测试类stillRunning().

// Inside your test
[TestMethod]
public void no_one_should_be_logged_in()
{
    _atm = new AtmThatImmediatelyShutsDown();

    this.SetupForCancelledUser();

    _atm.Start();

    Assert.IsNull(_atm.CurrentUser);
}

class AtmThatImmediatelyShutsDown : AtmMachine {
    protected override bool stillRunning() {
        return false;
    }
}

另一个选择是将条件注入可以模拟的类/接口.这是你的选择.

其次,为简单起见,我会将该循环的内容提取到一个具有更高可见性的方法中,以允许在循环中测试代码.

// In your AtmMachine
public void Start()
{
    _shouldContinue = true;

    while (stillRunning())
    {
        processCommands();
    }
}

public void processCommands() {
    ...
}

现在,您可以直接调用该processCommands()方法并跳过所有循环.

希望有所帮助!

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