How do I enforce exception message with ExpectedException attribute

@rcravens is correct - the second param is a message that is printed if the test fails. What I've done to work around this is craft my tests a little differently. Admittedly, I don't love this approach, but it works.

[TestMethod]
public void Validate()
{
    try
    {
        int.Parse("dfd");
    
        // Test fails if it makes it this far
        Assert.Fail("Expected exception was not thrown.");
    }
    catch (ArgumentNullException ex) // <-- Expected Exception class
    {
        Assert.AreEqual("blah", ex.Message);
    }
    catch (Exception ex) // All the other exceptions
    {
        Assert.Fail("Thrown exception was of the wrong type");
    }
}

That mstest second parameter is a message that is printed out when the test fails. The mstest will succeed if a formatexception is thrown. I found this post that may be useful

http://blogs.msdn.com/b/csell/archive/2006/01/13/expectedexception-might-not-be-what-you-ve-expected.aspx

We use this attribute all over the place and we clearly misunderstood the second parameter (shame on us).

However, we definitely have used it to check the exception message. The following was what we used with hints from this page. It doesn't handle globalization, or inherited exception types, but it does what we need. Again, the goal was to simply RR 'ExpectedException' and swap it out with this class. (Bummer ExpectedException is sealed.)

public class ExpectedExceptionWithMessageAttribute : ExpectedExceptionBaseAttribute
{
    public Type ExceptionType { get; set; }

    public string ExpectedMessage { get; set; }

    public ExpectedExceptionWithMessageAttribute(Type exceptionType)
    {
        this.ExceptionType = exceptionType;
    }

    public ExpectedExceptionWithMessageAttribute(Type exceptionType, string expectedMessage)
    {
        this.ExceptionType = exceptionType;
        this.ExpectedMessage = expectedMessage;
    }

    protected override void Verify(Exception e)
    {
        if (e.GetType() != this.ExceptionType)
        {
            Assert.Fail($"ExpectedExceptionWithMessageAttribute failed. Expected exception type: {this.ExceptionType.FullName}. " +
                $"Actual exception type: {e.GetType().FullName}. Exception message: {e.Message}");
        }

        var actualMessage = e.Message.Trim();
        if (this.ExpectedMessage != null)
        {
            Assert.AreEqual(this.ExpectedMessage, actualMessage);
        }

        Debug.WriteLine($"ExpectedExceptionWithMessageAttribute:{actualMessage}");
    }
}