In our efforts to refactor test cases and fixtures, we discovered that creating little languages for our major DomainObject''''''s dramatically improved the readability and conciseness of our test code. [-- RobMee, from TariffSystem]

I HaveThisPattern too. I find that diligent refactoring of test cases for objects that come under the repeated and intense scrutiny of large-grained tests (such as customer tests, but not exclusively) results in simple but flexible interfaces which lend themselves well to MetaData encodings, and are useful "just in time" in the context of production code as well as that of test code. -- LaurentBossavit

''Does 'little languages' mean an actual programming language, or is to do with nomenclature, or is it more of a metaphor? A concrete example would be helpful, although it might be impractical.''

Maybe this page is about a LittleLanguage (also called DomainSpecificLanguage.)