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 co

Answer 1

Use this little helper class:

public static class ExceptionAssert
{
    public static void Throws(Action action, string message)
        where TException : Exception
    {
        try
        {
            action();

            Assert.Fail("Exception of type {0} expected; got none exception", typeof(TException).Name);
        }
        catch (TException ex)
        {
            Assert.AreEqual(message, ex.Message);
        }
        catch (Exception ex)
        {
            Assert.Fail("Exception of type {0} expected; got exception of type {1}", typeof(TException).Name, ex.GetType().Name);               
        }
    }
}

Usage:

Foo foo = new Foo();
foo.Property = 42;

ExceptionAssert.Throws(() => foo.DoSomethingCritical(), "You cannot do anything when Property is 42.");

The advantage of explicit catching exceptions is that teh test does not succeed when another member (e.g. during the initialization) throws the exception.