c# - Moq - 为构造函数注入(inject)对象创建模拟实例

Question

问题

我想为 Credentials 类创建一个单元测试，在执行 Calculate() 方法后验证给定凭据的密码是否等于由实现 IPasswordCalculator 接口(interface)的对象。

实际上，我创建的模拟对象在调用 Calculate(ICredentials) 方法时返回 string.Empty 值，而不是 Pa$$w0rd，那将是期望的返回。

然后...

• 如何在无需手动创建 stub 类的情况下实现此测试？
• 如何在模拟对象上定义回调方法以始终返回 Pa$$w0rd？

提前致谢。

代码

IPasswordCalculator 接口(interface)

/// <summary>
///     The password calculator interface.
/// </summary>
public interface IPasswordCalculator
{
    /// <summary>
    /// Calculates the user password using 
    /// <paramref name="credentials"/> instance.
    /// </summary>
    /// <param name="credentials">
    /// <see cref="ICredentials"/> to perform the calculation.
    /// </param>
    void Calculate(ICredentials credentials);
}

ICredentials 接口(interface)

/// <summary>
///     The Credentials interface.
/// </summary>
public interface ICredentials
{
    /// <summary>
    ///     Gets or sets the user password.
    /// </summary>
    string Password { get; set; }

    /// <summary>
    ///     Gets the user name.
    /// </summary>
    string Username { get; }

    /// <summary>
    ///     Calculates the password.
    /// </summary>
    void Calculate();
}

凭证实现

/// <summary>
///     User credentials.
/// </summary>
public sealed class Credentials : ICredentials
{
    /// <summary>
    ///     Initializes a new instance of the <see cref="Credentials" /> class.
    /// </summary>
    /// <param name="passwordCalculator">
    ///     The credentials calculator.
    /// </param>
    /// <param name="username">
    ///     The user name.
    /// </param>
    public Credentials(IPasswordCalculator passwordCalculator, string username)
    {
        this.Calculator = passwordCalculator;
        this.Username = username;
        this.Password = string.Empty;
    }

    /// <summary>
    ///     Calculates the password.
    /// </summary>
    public void Calculate()
    {
        if (null != this.Calculator)
        {
            this.Calculator.Calculate(this);
        }
    }
}

测试

    /// <summary>
    /// Calculate should set password value expected using calculator.
    /// </summary>
    [TestMethod]
    public void CalculateShouldSetPasswordValueExpectedUsingCalculator()
    {
        ICredentials credentials = null;
        var repo = new MockRepository(MockBehavior.Default);
        var mock = repo.Create<IPasswordCalculator>();
        mock.Setup(x => x.Calculate(credentials))
            .Callback(() => { credentials.Password = "Pa$$w0rd"; });

        IPasswordCalculator calculator = mock.Object;

        credentials = new Credentials(calculator, "Me");
        credentials.Calculate();

        Assert.AreEqual("Pa$$w0rd", credentials.Password);  // Fail
    }

Answer 1

您需要按以下方式设置模拟

mock.Setup(x => x.Calculate(It.IsAny<ICredentials>()))
    .Callback((ICredentials c) => { c.Password = "Pa$$w0rd"; });

因此你告诉它“无论你得到什么 ICredentials 作为 Calculate 方法的参数，将它的 Password 设置为 'Pa$$word '"