MSTest ThrowsException与异常对象有条件？

Question

我正在使用MSTest Assert.ThrowsException，但有时我想在抛出的异常对象上添加测试条件，例如检查消息是否提到特定短语，标识符，数据值或其他内容。

我发现的最佳解决方案是不使用Assert.ThrowsException的结构，但是使用try...catch：

bool success = false;
try
{
    // Code to be tested goes here...
    success = true;
}
catch (Exception e)
{
    Assert.IsInstanceOfType(e, typeof(DesiredExceptionClass));
    // Tests on e go here...
}
if (success)
    Assert.Fail($"Should have thrown {nameof(DesiredExceptionClass)}.");

有没有更好的办法？

“更好”是指更具可读性，更紧凑的代码，更少的“样板”。

Answer 1

我正在使用这种方式：

    Exception exception = null;
        try
        {
            // Code to be tested goes here...
        }
        catch (Exception e)
        {
            exception = e;
        }
        Assert.IsInstanceOfType(exception, typeof(DesiredExceptionClass));

Answer 2

当应该提出异常时，有一个pattern I have post in the past来验证额外的期望。

您似乎正在尝试减少“Boilerplate代码”，因此我创建了以下帮助程序类：

public static class ExceptionAssert
{
    /// <summary>
    /// Use this method if your UT is using <see cref="ExpectedExceptionAttribute"/> and you want to verify additional expectations
    /// </summary>
    /// <typeparam name="T">The expected exception type base</typeparam>
    /// <param name="action">Execute the unit to test</param>
    /// <param name="verifier">Verify the additional expectations</param>
    public static void AssertException<T>(Action action, Action<T> verifier) where T: Exception
    {
        try
        {
            action();
        }
        catch(T e)
        {
            verifier(e);
            throw;
        }
    }

    /// <summary>
    /// Use this method if your UT is not using <see cref="ExpectedExceptionAttribute"/> and you want to verify additional expectations
    /// </summary>
    /// <typeparam name="T">The expected exception type base</typeparam>
    /// <param name="action">Execute the unit to test</param>
    /// <param name="verifier">Verify the additional expectations</param>
    /// <param name="allowDriven">Indicates if the raised exception can be an instance of driven class</param>
    public static void AssertExceptionWithoutExcepctedExceptionAttribute<T>(Action action, Action<T> verifier, bool allowDriven = true) where T : Exception
    {
        try
        {
            action();
            Assert.Fail("No Exception raised");
        }
        catch (T e)
        {
            if (!allowDriven && e.GetType() != typeof(T))
            {
                Assert.Fail($"The raised exception :: {e.GetType()} is a driven instance of :: {typeof(T)}");
            }
            verifier(e);
        }
    }
}

现在您可以执行以下某个UT：

[TestMethod]
[ExpectedException(typeof(Exception), AllowDerivedTypes = true)] // change the attribute settings
public void Foo()
{
    // do arrange:

    ExceptionAssert.AssertException<Exception>(() => // change "Exception" to the required exception type or left it as any exception
    {
        // do the act:

    }, exception =>
     {
         // do you asserts statements:
     });
}

[TestMethod]
public void FooBar()
{
    // do arrange:

    ExceptionAssert.AssertExceptionWithoutExcepctedExceptionAttribute<Exception>(() => // change "Exception" to the required exception type or left it as any exception
    {
        // do the act:

    }, exception =>
    {
        // do you asserts statements:
    }, false);
}

BTW，IMO除了他的类型/驱动之外你永远不应该验证异常本身（或者如果它是带有附加信息的自定义异常），因为你的代码永远不会依赖于他的MSG，调用堆栈等......我认为这是MS之所以没有增加 ExpectedExceptionAttribute验证MSG的能力。