If you get an error such as:

Check to see if you have any models declaring themselves as DataMapper::Resource but WITHOUT any property declarations.

No meaningful error is reported for this case at the moment (with HEAD as of last night) so it’s a weird one to debug – especially if you generate a bunch of model classes ahead of defining their behavior.

I’ve been having a blast with Merb and DataMapper lately.

Like everyone else who prefers clean over clever and true pragmatism over dogma, I prefer Merb over some of the other options out there for day to day Web apps.

That said, I’ve not done any major work with the two yet. I have some of my long-shelved personal apps being rewritten/written on Merb master and DataMapper master, but I am kind of holding off on larger commitments until the 1.0 release.

If you haven’t checked out Merb and Datamapper > 0.9 you should.

I’m even coming around on rSpec, though I still prefer xUnit style testing because the language and flow is the same across all the types of development I do (PHP, Ruby, Objective-C, Java).