# Test Case: LZ4 Sequential Read Correctness

**Test ID**: TC086-lz4-sequential-read

**G5 fixture contract**: Use [G5-MANUAL-SETUP.md](G5-MANUAL-SETUP.md).
Its generated paths, source comparisons, structured corruption offsets, and
cleanup rules supersede placeholder examples in this file.
**Category**: Compression
**Priority**: High

## Objective

Verify complete sequential reads of an LZ4-compressed file with two request
sizes against the original source bytes. Record timings only; repo22 exposes no
filesystem-specific DTrace provider and this test has no fixed throughput
threshold.

## Fixture

```sh
work=$(mktemp -d /tmp/repo22-tc086.XXXXXX)
tests/prepare_error_fixtures.sh "$work/fixtures"
dump.erofs -s "$work/fixtures/valid-lz4.erofs"
dump.erofs --path=/compressed.bin -e "$work/fixtures/valid-lz4.erofs"
```

The dump must identify `/compressed.bin` as compressed LZ4 data with real
physical extents.

## FreeBSD Procedure

```sh
mkdir "$work/mnt"
unit=$(mdconfig -a -t vnode -f "$work/fixtures/valid-lz4.erofs")
mount -t erofs -o ro "/dev/$unit" "$work/mnt"

expected=$(sha256 -q "$work/fixtures/source/compressed.bin")
actual=$(sha256 -q "$work/mnt/compressed.bin")
test "$actual" = "$expected"

/usr/bin/time -p dd if="$work/mnt/compressed.bin" \
  of="$work/read-4k.bin" bs=4096 2>"$work/time-4k.txt"
cmp "$work/fixtures/source/compressed.bin" "$work/read-4k.bin"
/usr/bin/time -p dd if="$work/mnt/compressed.bin" \
  of="$work/read-1m.bin" bs=1048576 2>"$work/time-1m.txt"
cmp "$work/fixtures/source/compressed.bin" "$work/read-1m.bin"
cat "$work/time-4k.txt" "$work/time-1m.txt"

umount "$work/mnt"
mdconfig -d -u "${unit#md}"
```

## Expected Results

Both complete outputs compare byte-for-byte with the source and both hashes
match. Timing values are recorded with guest CPU, VM, and storage context; one
buffer size is not required to outperform the other.
