Are you working on LSP implementation? Maintaining a language support plugin? Or even creating your own compiler? Then quality is of paramount importance. The concept of an extendable and straightforward use-case test engine allows you to provide code examples along with their expected results, use them in test-driven development for the parsers, and then automate the syntax and semantic output checks. It uses the magic of domain-specific languages and simplifies defining the use-cases for your parser.