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• +Correctly returns the exact same in-flight Promise for concurrent calls using the same key.
• +Caches successful results with an expiration timestamp and retries after failures by deleting rejected entries.
• +Installs the pending entry before the deferred handler executes, avoiding a concurrency race.
• +14 more

• ∅The test snippets do not define or identify the expected `assert` and `assertRejects` helpers, so they are not fully…
• ∅There is no proactive cleanup of expired entries that are never accessed again, although this limitation is explicitly…
• ∅No eager TTL cleanup (only noted, not required)
• +1 more

Best improvement: Provide a small self-contained test harness defining `assert` and `assertRejects` so the listed tests can be run directly without relying on unspecified globals.

• +Correctly deduplicates concurrent calls by storing and returning the same wrapper Promise.
• +Keeps in-flight entries valid regardless of handler duration, starts the TTL after successful completion, and removes…
• +Uses Promise identity checks to prevent stale completion or rejection handlers from modifying a newer entry.
• +14 more

• ∅The tests are prose scenarios rather than executable TypeScript assertions, so they cannot directly verify the…
• ∅There is no test for edge cases such as ttlMs equal to zero or very large TTL values.
• ∅Executable test code (only narrative test plans); acceptable given the string-array output format but less immediately…
• +1 more

Best improvement: Replace timer-based eviction with lazy expiration checks, or schedule long TTLs in bounded chunks, and provide executable TypeScript tests with concrete assertions rather than prose descriptions.