test code v1

tests/TC107-zstd-level22.md

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+# Test Case: zstd Compression Level 22
+
+**Test ID**: TC107-zstd-level22  
+
+**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**: Medium  
+**Regression**: None
+
+## Objective
+Verify zstd compressed data path with level 22 (maximum) compression.
+
+## Preconditions
+- EROFS image created with zstd level 22: `mkfs.erofs -zzstd,level=22 test.img src/`
+- Large test files (multi-MB)
+- FreeBSD 13.0+ with libzstd
+
+## Test Steps
+1. Create image with zstd level 22 compression
+2. Attach and mount: `unit=$(mdconfig -a -t vnode -f test.img); mount -t erofs -o ro /dev/${unit} /mnt`
+3. Read large files sequentially
+4. Test random access
+5. Monitor memory usage during decompression
+
+## Expected Results
+- All files decompress correctly
+- Maximum compression ratio for zstd
+- Acceptable decompression speed
+- Stable memory usage
+
+## Verification Method
+- Checksums match original files
+- Compression ratio > level 15
+- Decompression throughput > 100 MB/s
+- No memory leaks
+
+## Cleanup
+```sh
+umount /mnt
+mdconfig -d -u "${unit}"
+```
+
+## Notes
+Tests feature 59: zstd compressed data path with maximum compression.