the Langium services for the language with code actions
A function to easily test a single code action on the given invalid 'input'. This function expects, that 'input' contains exactly one validation problem with the given 'diagnosticCode'. If 'outputAfterFix' is specified, this functions checks, that the diagnostic comes with a single code action for this validation problem. After applying this code action, 'input' is transformed to 'outputAfterFix'.
Optional
options: ParseHelperOptions
This is a helper function to easily test code actions (quick-fixes) for validation problems.