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+# Test Case: DEFLATE and ZSTD Partial References
+
+**Test ID**: TC143-deflate-zstd-partial-reference
+
+**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**: Critical
+**Regression**: Non-LZ4 partial-reference decoding
+
+## Objective
+Verify full and partial-reference decoding for raw DEFLATE and ZSTD streams,
+including exact full-file SHA256, cross-extent reads, random reads, and
+corrupted-stream `EIO` behavior.
+
+## Preconditions
+- FreeBSD 15 guest.
+- ZSTDIO-enabled repo22 module for the ZSTD cases.
+- Deterministic full-index fixtures whose layout parser proves:
+  - the full file points at a complete compressed stream;
+  - the partial file reuses that physical stream;
+  - the reused HEAD record has `Z_EROFS_LI_PARTIAL_REF` (`0x8000`) set;
+  - the reused first NONHEAD record has the complete source pcluster's
+    `D0_CBLKCNT`, not the partial file's original compressed-block count;
+  - the partial file's logical length is shorter than the source stream's
+    decompressed length.
+- Corrupted copies produced only after locating the target compressed extent;
+  do not use a blind image offset.
+
+## Layout Proof
+```sh
+dump.erofs -s deflate-partial-ref.erofs
+dump.erofs --path=/a.dat -e deflate-partial-ref.erofs
+dump.erofs --path=/b.dat -e deflate-partial-ref.erofs
+dump.erofs -s zstd-partial-ref.erofs
+dump.erofs --path=/a.dat -e zstd-partial-ref.erofs
+dump.erofs --path=/b.dat -e zstd-partial-ref.erofs
+```
+
+The byte-level fixture record must assert the original NID, map-header offset,
+HEAD record, pblk, and checksum before setting the partial-reference bit or
+redirecting a pblk.
+
+## Test Steps
+1. Mount the DEFLATE image and hash `/a.dat` and `/b.dat` completely.
+2. Read a range crossing a known DEFLATE logical extent boundary.
+3. Read another non-aligned random range and compare it byte-for-byte with the
+   source.
+4. Repeat steps 1-3 for ZSTD.
+5. Mount each corrupted copy and read the targeted file through a small C
+   errno probe.
+6. Compare pre/post `dmesg` and active `vmstat -m` EROFS allocations.
+
+The G5 DEFLATE partial is 100000 bytes because erofs-utils 1.8.6 splits the
+1 MiB DEFLATE source according to the 32 KiB DEFLATE window. It reuses the
+first 17-block source pcluster and uses offsets 65500/2048 and 90000/4096.
+The ZSTD partial is 700000 bytes and uses these checks:
+
+```sh
+dd if=/mnt/repo22/b.dat of=/tmp/guest bs=1 skip=122900 count=512 status=none
+dd if=source-b.dat of=/tmp/source bs=1 skip=122900 count=512 status=none
+cmp /tmp/guest /tmp/source
+
+dd if=/mnt/repo22/b.dat of=/tmp/guest bs=1 skip=524287 count=4097 status=none
+dd if=source-prefix-b.dat of=/tmp/source bs=1 skip=524287 count=4097 status=none
+cmp /tmp/guest /tmp/source
+```
+
+## Expected Results
+- Full DEFLATE and ZSTD streams require complete output and stream completion.
+- Partial references succeed after producing the requested logical prefix;
+  they do not require the reused source frame to finish.
+- Complete SHA256 and every boundary/random byte comparison match.
+- Targeted corruption returns read errno 5 (`EIO`), with no leaked active
+  allocation, panic, or trap.
+- `control.bin` in each corrupted image remains byte-identical to its source.
+
+## Cleanup
+Unmount each image, detach every md unit, remove temporary range outputs, and
+unload the module by its `kldstat` ID.