Test Case: LZ4 Compression Basic Support

Test ID: TC084-lz4-basic

G5 fixture contract: Use 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: None

Objective

Verify basic LZ4 compression support for reading compressed files.

Preconditions

EROFS image with LZ4 compression: test-lz4-basic.erofs
Test file: /files/test-lz4.txt (1MB, highly compressible)
Mount point: /mnt/test

Test Steps

Mount the LZ4-compressed image:
```
mount -t erofs /dev/md0 /mnt/test
```

Read entire compressed file:

cat /mnt/test/files/test-lz4.txt > /tmp/output.txt

Verify file size:

stat -f %z /mnt/test/files/test-lz4.txt

Compare with reference (uncompressed):
```
cmp /tmp/output.txt /tmp/reference.txt
```

Test multiple LZ4-compressed files:

for f in /mnt/test/files/lz4-*.txt; do
  cat "$f" > /dev/null
done

Expected Results

Step 1: Mount succeeds
Step 2: File read successfully, decompressed transparently
Step 3: Size matches original uncompressed size (1048576 bytes)
Step 4: Files identical (cmp returns 0)
Step 5: All LZ4 files read without errors

Verification Method

Verify decompression transparent to application
Confirm data integrity after decompression
Test LZ4 decompression performance acceptable
Verify compressed file sizes smaller than uncompressed

Cleanup

umount /mnt/test
mdconfig -d -u md0
rm /tmp/output.txt

Notes

LZ4 provides fast decompression with moderate compression ratio
EROFS uses LZ4 for general-purpose compression
Related tests: TC003 (LZ4 compressed read), TC085 (large files)

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