or... they create their own internal DSLs - customers and internal people use those - and everyone spends years thinking about the 'custom DSL' way. Developing

or... they create their own internal DSLs - customers and internal people use those - and everyone spends years thinking about the 'custom DSL' way. Developing any sort of automated testing around your own custom language basically becomes impossible. I did some work for a place where, they embedded groovy as their 'write custom rules stuff from the UI' language - that was at least easier to reason about, and to debug/test offline (not automated, but somewhat easier than a DSL that only runs inside the system).