unit testing - In MSTest, How can I verify exact error message using [ExpectedException(typeof(ApplicationException))]

Question

Using MSTest how can I verify the exact error message coming from a test method? I know [ExpectedException(typeof(ApplicationException), error msg)] doesn't compare the error message coming from my test method, though in other unit test framework it is doing.

One way to solve this problem is to write my unit test using some try catch block, but again I need to write 4 lines more.

Is there any smartest way to check the error message.

Cheers, Pritam

Answer 1

You can create your own ExpectedException attribute where you can Assert the message of the Exception that was thrown.

Code

namespace TestProject
{
    public sealed class MyExpectedException : ExpectedExceptionBaseAttribute
    {
        private Type _expectedExceptionType;
        private string _expectedExceptionMessage;

        public MyExpectedException(Type expectedExceptionType)
        {
            _expectedExceptionType = expectedExceptionType;
            _expectedExceptionMessage = string.Empty;
        }

        public MyExpectedException(Type expectedExceptionType, string expectedExceptionMessage)
        {
            _expectedExceptionType = expectedExceptionType;
            _expectedExceptionMessage = expectedExceptionMessage;
        }

        protected override void Verify(Exception exception)
        {
            Assert.IsNotNull(exception);

            Assert.IsInstanceOfType(exception, _expectedExceptionType, "Wrong type of exception was thrown.");

            if(!_expectedExceptionMessage.Length.Equals(0))
            {
                Assert.AreEqual(_expectedExceptionMessage, exception.Message, "Wrong exception message was returned.");
            }
        }
    }
}

Usage

[TestMethod]
[MyExpectedException(typeof(Exception), "Error")]
public void TestMethod()
{
    throw new Exception("Error");
}