Developed multi-file compile testing support for the kotest/kotest repository, focusing on the kotest-assertions-compile module. Extended the existing shouldCompile and shouldNotCompile APIs to accept lists of files, enabling comprehensive cross-file compile-time validation. This enhancement addressed the need for robust testing across multiple Kotlin source files, reducing the risk of cross-file regressions and improving overall test coverage. The work involved compiler development and advanced testing techniques in Kotlin, resulting in a repository-level improvement that increased developer confidence when validating compile-time assertions. The approach emphasized maintainability and scalability for future testing scenarios involving multiple source files within the project.