As a User I want to inject external data sets as variables and access them from the test scenarios so that I can create tests that are driven by data

Acceptance Criteria
- Grammar should be available to define input data sources
- Data need to be entered as csv files. they will be converted to object collecttions

No files, tests, or entry points are named. Start by locating the grammar definitions and test-scenario variable handling, then determine how CSV input should become object collections and how scenarios access them; done means the grammar accepts data sources and data-driven scenarios work with CSV files.

Written by the indexing model from the issue text.