Context

Historically, Codexis test code has used a mix of approaches for creating temporary files and directories, including direct calls to File.mkdir_p!, File.write!, and hardcoded paths like tmp, tmp_test, or test/fixtures. This has led to:

• Permission errors on CI and some developer machines
• Inconsistent or incomplete cleanup of temp files/dirs
• Tests that are not portable across environments
• Occasional pollution of the project root or persistent test data directories

Decision

All test code in Codexis must use the Briefly library (or a project-standard wrapper around Briefly) for creating and managing temporary files and directories.

• No test may write to the project root, tmp, or test/fixtures directly.
• All temp dirs/files must be created with Briefly.create/1 (or a shared fixture that uses Briefly).
• Persistent test data (e.g., test/fixtures) must be read-only and never written to or cleaned up by tests.
• All test helpers/fixtures must be refactored to use Briefly for temp resources.
• Manual cleanup (on_exit for temp dirs/files) should be removed where Briefly is used, as Briefly handles cleanup automatically.

Consequences

• Positive:
  • No more permission errors due to unwritable temp locations
  • Automatic, reliable cleanup of all temp files/dirs after tests
  • Tests are portable and robust across all environments (local, CI, sandboxed)
  • Easier maintenance and clearer test setup/teardown
• Negative:
  • Requires refactoring of existing test code and helpers
  • Developers must learn and consistently use Briefly patterns

References

• Briefly documentation
• ADR-0012: Test-Driven Design
• ADR-0022: Elixir Module Structure
• ADR-0029: Elixir Implementation
• Cursor Rule: Elixir Test Temp Files (if exists)