Again, it would be nice to be able to have some construct like generatesFile().containing("someString").  

I think the and() stuff would be linguistically hard, because you switch to testing the file contents.  Or a way to capture the generated file so it can be interrogated elsewhere.  I can't think of a nice way just now, but it's worth mulling over.  Capture seems less "in the flow" than further predicates, but the value for complication trade-off can get really bad here. :(