Look on my works, ye Mighty, and despair!

NHamcrest is supported out of the box with MbUnit, but there’s nothing stopping you using it with any other framework.

You just need to write the shim code, i.e. Assert.That.

For example, with NUnit it would look something like this:

public static void That<T>(T actual, IMatcher<T> matcher, string message, params object[] args)
{
	if (matcher.Matches(actual))
		return;
	
	var writer = new TextMessageWriter(message, args);

	WriteExpected(matcher, writer);

	WriteActual(actual, matcher, writer);

	throw new AssertionException(writer.ToString());
}

private static void WriteExpected(ISelfDescribing matcher, TextWriter writer)
{
	writer.Write(TextMessageWriter.Pfx_Expected);
	var description = new StringDescription();
	matcher.DescribeTo(description);
	writer.Write(description.ToString());
	writer.WriteLine();
}

private static void WriteActual<T>(T actual, IMatcher<T> matcher, TextWriter writer)
{
	writer.Write("  But ");
	var mismatchDescription = new StringDescription();
	matcher.DescribeMismatch(actual, mismatchDescription);
	writer.Write(mismatchDescription.ToString());
	writer.WriteLine();
}

For XUnit:

public static void That<T>(T actual, IMatcher<T> matcher)
{
	if (matcher.Matches(actual))
		return;

	var description = new StringDescription();
	matcher.DescribeTo(description);

	var mismatchDescription = new StringDescription();
	matcher.DescribeMismatch(actual, mismatchDescription);

	throw new MatchException(description.ToString(), mismatchDescription.ToString(), null);
}

public class MatchException : AssertActualExpectedException
{
	public MatchException(object expected, object actual, string userMessage) : base(expected, actual, userMessage)
	{
	}
}

And, for completeness, here’s the MbUnit version:

        public static void That<T>(T item, IMatcher<T> matcher, string messageFormat, params object[] messageArgs)
        {
            AssertionHelper.Verify(() =>
            {
                if (matcher.Matches(item))
                    return null;

                var description = new StringDescription();
                var mismatchDescription = new StringDescription();

                matcher.DescribeTo(description);
                matcher.DescribeMismatch(item, mismatchDescription);

                return new AssertionFailureBuilder("Expected " + description)
                    .SetMessage(messageFormat, messageArgs)
                    .AddLabeledValue("Expected", description.ToString())
                    .AddLabeledValue("But", mismatchDescription.ToString())
                    .ToAssertionFailure();
            });           
        }