I like Moq.  For me it has made unit testing almost enjoyable, similar to how jQuery makes writing javascript more bearable.

Today I ran into an issue.  I'm mocking System.Data.IDataReader (I'm old school okay, but I'm writing unit tests, so give me a break).  So in my code, I call the Read() method of IDataReader until it returns false.

while (reader.Read())
{
	// old man code here
}

Moq is great when you setup calls to a method that are somewhat unique.  But in this case, each successive call has the same arguments (no argument).  So how can I get Read() to return true the first time, then false on any call after that?  Well it's probably in the Moq documentation somewhere, but forget that.  Here's my solution:

var readerMock = new Mock<System.Data.IDataReader>();
int row = 0;
readerMock.Setup(x => x.Read()).Returns(row++ == 0);

Except that doesn't seem to work quite right, since it evaluates upon setup, not on invocation.  Or something.  This seems to work:

var readerMock = new Mock<System.Data.IDataReader>();
int row = 0;
readerMock.Setup(x => x.Read()).Returns(() => row++ == 0);

Now it gets evaluated when it is invoked I think.  It works at any rate.  Plus the inclusion of a lambda expression gives the added benefit of making it appear that I know what I'm doing.