test(fifo): strengthen test assertions for intellectual honesty

[ryanbreen]

Summary

Address validation findings from technical implementation review. Remove fallback acceptance patterns that would pass broken implementations.

Changes

Phase 8 (EOF test)

• Before: Accepted EAGAIN as alternative to EOF
• After: Only EOF (0) is valid; EAGAIN is now a failure
• Why: POSIX requires read to return 0 when all writers close. EAGAIN means "try again" - the opposite of EOF.

Phase 9 (EPIPE test)

• Before: Accepted write success as "deferred EPIPE"
• After: Write success is now a failure
• Why: If write succeeds after reader closes, data is lost. EPIPE must be returned immediately.

Phase 7 (Blocking read)

• Before: total >= 10 and silent error handling in child
• After: total == 10 (exact) and proper error reporting
• Why: Child writes exactly 10 bytes; weak assertion wouldn't catch partial reads or garbage data.

Validation Context

These issues were identified by the collaboration:technical-implementation-validation skill which scored:

• Technical Accuracy: C+ (core functionality tested, gaps in coverage)
• Intellectual Honesty: D+ (gaming patterns detected)

The "criteria reduction" patterns in Phase 8 and 9 were the primary honesty concerns.

Test plan

• Build succeeds
• CI passes with stricter assertions

🤖 Generated with Claude Code