build-and-test

To build the Motoko compiler and run regression tests, use the nix-direnv environment to execute `dune build --root src` for compilation, then run the `test-runner` in batch mode from the repository root to validate your OCaml changes.

The correct way to run the Motoko test-runner for fast fail suites is to execute `test-runner -baf fail/` from the repository root. Batch mode and acceptance flags automatically update expected outputs instead of requiring manual file edits.

To update expected test outputs in the Motoko compiler repository, use the acceptance flag (`-a`) with the `test-runner` command. This automatically applies the new expected outputs rather than manually editing the test files.

Yes, you need nix-direnv to compile `moc` and run dune build targets. The deterministic build workflow relies on the repo's dune configuration combined with the nix-direnv environment to ensure correct compilation and avoid tooling inconsistencies.

Motoko regression tests fail outside the repository root because the `test-runner` workflow must be executed from the top level. Running it elsewhere breaks the required relative paths for test categories like `fail/`, `run/`, and `run-drun/`.

You can run category-appropriate test suites with the Motoko test-runner by specifying directories like `fail/`, `run/`, and `run-drun/`. This targets specific regression tests based on your compiler development needs.