test: remove check tail assertion from correctness test

[quettabit]

No description provided.

[greptile-apps]

Greptile Summary

Removes the post-run check_tail assertion (tail.seq_num == TOTAL_RECORDS) from the concurrent producer/consumer correctness test. As clarified in the prior thread, this assertion was unsound because retried appends can leave duplicate records on a persistent stream, causing tail.seq_num to exceed TOTAL_RECORDS and spuriously fail the test.

• The remaining consumer-side assertions (last_seq_num == TOTAL_RECORDS - 1, observed_records == TOTAL_RECORDS, highest_contiguous_index == TOTAL_RECORDS - 1, and per-record gapless seq_num checks) are sufficient to validate that exactly 1024 records were read back without gaps, which is the core correctness guarantee the test is designed to prove.
• No logic changes to production code; test-only diff.

Confidence Score: 5/5

Safe to merge — removes one assertion from a test file with no production code changes.

The deleted check_tail assertion was logically incorrect on persistent streams where retry-driven duplicates push tail.seq_num beyond TOTAL_RECORDS. The remaining consumer-side assertions still fully cover the gapless-read invariant the test was designed to verify, so no coverage gap is introduced.

No files require special attention.

Important Files Changed

Filename	Overview
tests/test_correctness.py	Removed post-run check_tail assertion whose equality condition was incorrect when retries cause duplicate records on the stream; remaining consumer-side assertions still fully validate gapless read correctness.

Sequence Diagram

sequenceDiagram
    participant Test as Test (TaskGroup)
    participant Producer as append_records()
    participant Consumer as read_records()
    participant Stream as S2Stream

    par concurrent tasks
        Producer->>Stream: "producer.submit(Record(body=str(i))) x 1024"
        Stream-->>Producer: ticket (per record)
        Producer->>Stream: await ticket x 1024
        Stream-->>Producer: "ack.seq_num >= 0"

        Consumer->>Stream: "read_session(start=SeqNum(0), limit=count(1024), wait=60)"
        Stream-->>Consumer: batches of records
        Consumer->>Consumer: "assert seq_num == last_seq_num + 1 (gapless)"
        Consumer->>Consumer: "assert 0 <= index < 1024 (valid body)"
        Consumer->>Consumer: "assert index <= highest_contiguous_index + 1"
    end

    Note over Test: After TaskGroup completes
    Consumer->>Consumer: "assert highest_contiguous_index == 1023"
    Consumer->>Consumer: "assert last_seq_num == 1023"
    Consumer->>Consumer: "assert observed_records == 1024"
    Note over Test: check_tail assertion removed - tail.seq_num may exceed 1024 when retries produce duplicates

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_{Reviews (2): Last reviewed commit: "initial commit" | Re-trigger Greptile}

[quettabit]

@greptileai addressed your comment. pls review again and update your score.