Cross-Language Testing

One of CompressKit's key features is identical binary formats across all language implementations. This enables seamless cross-language encoding and decoding.

Test Methodology

Our CI pipeline verifies correctness across all 12 possible encoding/decoding combinations:

4 algorithms × 3 languages = 12 implementations
12 encoders × 3 decoders = 36 cross-language pairs

Test Matrix

Encode ↓ / Decode →	C++	Go	Rust
C++	✅	✅	✅
Go	✅	✅	✅
Rust	✅	✅	✅

How It Works

Each algorithm uses a strictly defined binary format:

Huffman Example

+----------+-------------------+---------------+
|  Magic   | Frequency Table   | Encoded Data  |
| (4 bytes)| (257 × 4 bytes)   | (variable)    |
+----------+-------------------+---------------+
| "HFMN"   | uint32[257]       | bit stream    |
+----------+-------------------+---------------+

All three implementations write this exact structure:

• Same magic bytes (HFMN)
• Same endianness (little-endian)
• Same table layout
• Same bit stream encoding

Running Cross-Language Tests

Manual Verification

# Generate test data
dd if=/dev/urandom of=test.bin bs=1M count=1

# C++ encode → Go decode
./algorithms/huffman/cpp/huffman_cpp encode test.bin encoded.huf
./algorithms/huffman/go/huffman_go decode encoded.huf restored.bin
diff test.bin restored.bin  # Should produce no output

# Go encode → Rust decode
./algorithms/huffman/go/huffman_go encode test.bin encoded.huf
./algorithms/huffman/rust/huffman_rust decode encoded.huf restored.bin
diff test.bin restored.bin

# Try any combination:
# C++ ↔ Go, C++ ↔ Rust, Go ↔ Rust
# Works for all 4 algorithms

Automated Testing

make test

This runs the full cross-language test suite across all algorithms.

File Format Specifications

Detailed format specifications are available in the specs directory:

• Core Architecture Specs
• Cross-Language Testing Specs

Why Cross-Language Matters

1. Data Portability: Encode data in one environment, decode in another
2. Incremental Migration: Gradually move from one language to another
3. Testing Verification: Multiple independent implementations catch bugs
4. Learning: Compare how the same algorithm is implemented differently

Known Limitations

Algorithm	Limitation	Workaround
Range Coder	Decode performance degrades >500 KiB	Use smaller chunks

Reporting Issues

If you find cross-language incompatibilities:

1. Test with diff to verify binary mismatch
2. Check file headers with xxd -l 20 encoded.huf
3. Report to GitHub Issues with:
   • Algorithm name
   • Encode language
   • Decode language
   • Input file type