您可以对没有返回类型的 void 方法进行单元测试吗？

Question

我有这个 void 方法，我想对其进行单元测试，但不幸的是，我在这方面没有太多经验。

public void findOccuranceMethod()
{
    string str = "The Haunting of Hill House!";
    Console.WriteLine("String: " + str);
    string occurString = "o";
    string replaceString = "MDDS";

    var array = str.Split(new[] { occurString }, StringSplitOptions.None);
    var count = array.Length - 1;
    string result = string.Join(replaceString, array);

    Console.WriteLine("String after replacing a character: " + result);
    Console.WriteLine("Number of replaces made: " + count);
    Console.ReadLine();

}

这是我尝试测试的 TestClass，但在我运行它时它一直在加载：

[TestMethod()]
public void findOccuranceMethodTest()
{
    // Arrange
    string expected = "The Haunting MDDSf Hill HMDDSuse!";

    // Act
    var result = new findOccurance();

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

Answer 1

为可测试性正确重构代码

对这种逻辑进行编码和单元测试的正确方法是：

public class SomeProductionClass 
{
    public string findOccuranceMethod(string str) 
    {
        string occurString = "o";
        string replaceString = "MDDS";
        var array = str.Split(new[] { occurString }, StringSplitOptions.None);
        string result = string.Join(replaceString, array);

        return result;
    }
}

[TestMethod()]
public void findOccuranceMethodTest()
{
    // Arrange
    string expected = "The Haunting MDDSf Hill HMDDSuse!";
    var productionClass = new SomeProductionClass();

    // Act
    var result = productionClass.findOccuranceMethod("The Haunting of Hill House!");

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

如何测试原代码

如果由于某种原因您无法控制生产代码，有两种选择：

• 用抽象替换Console

• 将标准输入/输出重新分配给自定义流：这是最不受欢迎的选项，因为它使设置/清理更加复杂，并且会干扰测试运行器。

在任何一种情况下，我们都不得修改被测代码以引入单独的测试/生产分支。例如，“如果在测试中运行，则执行 A，否则执行 B”——在这种情况下，我们实际上并不是在测试生产代码，而是在测试它的不同分支。

用抽象替换控制台

这里我们介绍IConsole作为System.Console的替代品：

public interface IConsole
{
    void WriteLine(string s);
    void ReadLine(); // void is enough for this example
}

// for use in production
public class RealConsole : IConsole
{
    public void WriteLine(string s)
    {
        Console.WriteLine(s); 
    }
    public void ReadLine()
    {
        Console.ReadLine();
    }
}

// for use in unit tests
public class TestConsole : IConsole
{
    public void WriteLine(string s)
    {
        Contents.Add(s);
    }
    public void ReadLine()
    {
    }

    public List<string> Contents { get; } = new List<string>();
}

生产代码将保持原帖中的状态，只是现在它使用 _console 作为依赖项：

public class SomeProductionClass
{
    private readonly IConsole _console;

    public SomeProductionClass(IConsole console)
    {
        _console = console;
    }

    public void findOccuranceMethod()
    {
        string str = "The Haunting of Hill House!";
        _console.WriteLine("String: " + str);
        string occurString = "o";
        string replaceString = "MDDS";

        var array = str.Split(new[] { occurString }, StringSplitOptions.None);
        var count = array.Length - 1;
        string result = string.Join(replaceString, array);

        _console.WriteLine("String after replacing a character: " + result);
        _console.WriteLine("Number of replaces made: " + count);
        _console.ReadLine();
    }
}

测试代码是：

[TestMethod()]
public void findOccuranceMethodTest()
{
    // Arrange
    string expectedString = "The Haunting MDDSf Hill HMDDSuse!";
    int expectedCount = 2;
    var console = new TestConsole();
    var productionClass = new SomeProductionClass(console);

    // Act
    productionClass.findOccuranceMethod();

    // Assert
    Assert.AreEqual(3, console.Contents.Count);
    Assert.AreEqual("String: The Haunting of Hill House!", console.Contents[0]);
    Assert.AreEqual(
        $"String after replacing a character: {expectedString}", 
        console.Contents[1]);
    Assert.AreEqual(
        $"Number of replaces made: {expectedCount}", 
        console.Contents[2]);
}

Answer 2

如果您需要保留签名，您可以选择可选参数：

    public void optionSameSignature(Action<string> log = null, Func<string> read = null)
    {
        log = log ?? Console.WriteLine;
        read = read ?? Console.ReadLine;

        string str = "The Haunting of Hill House!";
        log("String: " + str);
        string occurString = "o";
        string replaceString = "MDDS";

        var array = str.Split(new[] { occurString }, StringSplitOptions.None);
        var count = array.Length - 1;
        string result = string.Join(replaceString, array);

        log("String after replacing a character: " + result);
        log("Number of replaces made: " + count);
        read();
    }

    public void Test()
    {
        List<string> lines = new List<string>();
        optionSameSignature(lines.Add, () => "");
    }

在更深层次上，输入和输出是一个技术细节，因此理想情况下，您应该尝试在没有技术细节的情况下拥有您的业务价值代码。这样的事情可能更接近您的实际需求：

    private static void mybusinessfunction(string input, out int count, out string result)
    {
        string occurString = "o";
        string replaceString = "MDDS";

        var array = input.Split(new[] { occurString }, StringSplitOptions.None);
        count = array.Length - 1;
        result = string.Join(replaceString, array);
    }