Platform-Safe Test Dependencies

• Status: Recorded
• Date: 2026-08-15
• Operator approval: Not applicable: nonarchitectural task record
• Context:
  • The first full macOS gate reached systemstat::System::mount_at from dashboard tests and aborted on an invalid raw-slice precondition inside the dependency before Rust could unwind.
  • The same workspace run exposed a CLI tail test that cancelled after a fixed delay without first observing the asynchronous resume-file write.
  • Both corrections already existed in later approved stack work but were required at the bottom boundary for independent validation.
• Decision:
  • Route dashboard disk usage through the existing ApiState test dependency seam, retaining the production systemstat implementation as the default and using a deterministic filesystem-aware provider in dashboard tests.
  • Run the CLI tail operation in a task, wait with a bounded deadline until the resume file is observable, then abort and verify cancellation and file contents.
• Consequences:
  • Dashboard tests no longer execute unsafe platform-specific dependency internals.
  • The tail test validates the event-to-resume-file contract instead of assuming a scheduler-dependent 200 ms completion window.
  • Production dashboard behavior is unchanged.
• Follow-up:
  • Drop duplicate hunks when the descendant API and CLI commits are replayed.
  • Keep platform and asynchronous dependencies injected or observed through deterministic boundaries in future tests.

Task Record

• Motivation:
  • Make the bottom stack boundary pass the repository-wide test gate deterministically on the operator’s macOS environment and Linux CI.
• Design notes:
  • The disk provider is a function pointer with a production default and a test-only replacement method, matching the approved descendant implementation.
  • Resume-file polling accepts only NotFound as transient; every other I/O error fails immediately and the total wait is capped at 30 seconds.
• Test coverage summary:
  • Re-ran just test with all workspace features after both corrections.
  • Both dashboard tests and run_with_cli_executes_select_action_and_tail passed in the complete workspace run.
  • just ci and all 101 just ui-e2e tests passed on the complete validation-foundation tree.
• Observability updates:
  • No runtime observability surface changed. Test failures now distinguish timeout, unexpected task exit, task failure, and filesystem errors.
• Status-doc validation:
  • Updated the ADR catalogue and documentation summary; no user-facing runtime documentation changed.
• Risk & rollback plan:
  • Revert both test-boundary changes together if they regress construction or cancellation semantics.
  • Do not restore direct platform probing in tests or fixed-delay cancellation without a deterministic replacement.
• Dependency rationale:
  • No dependency was added or changed.
• Stale-policy check:
  • Reviewed AGENTS.md and the Rust scoped instructions.
  • The correction tightens the existing dependency-injection rule; no contradiction or stale reference was introduced.