behavior-preservation-checker

Behavior Preservation Checker

Overview

Validate that a migrated or refactored codebase preserves the original behavior by automatically comparing runtime behavior, test results, execution traces, and observable outputs between two repository versions.

Core Workflow

1. Setup Repositories

Prepare both repositories for comparison:

# Clone or locate repositories
ORIGINAL_REPO=/path/to/original
MIGRATED_REPO=/path/to/migrated

# Ensure both are at comparable states
cd $ORIGINAL_REPO && git checkout main
cd $MIGRATED_REPO && git checkout main

2. Run Behavior Comparison

Use the comparison script to analyze behavioral differences:

python scripts/behavior_checker.py \
    --original $ORIGINAL_REPO \
    --migrated $MIGRATED_REPO \
    --output behavior_report.json

3. Review Results

Examine the generated report for:

• Test result differences
• Execution trace divergences
• Output mismatches
• Performance regressions
• API contract violations

4. Fix Deviations

Follow actionable guidance to resolve behavioral differences.

Comparison Methods

Method 1: Test-Based Comparison

Run the same test suite on both repositories and compare results:

Workflow:

1. Identify common test suite (or create equivalent tests)
2. Run tests on original repository
3. Run tests on migrated repository
4. Compare pass/fail status, assertions, and outputs

Example:

# Run on original
cd $ORIGINAL_REPO
pytest tests/ --json-report --json-report-file=original_results.json

# Run on migrated
cd $MIGRATED_REPO
pytest tests/ --json-report --json-report-file=migrated_results.json

# Compare
python scripts/compare_test_results.py \
    original_results.json \
    migrated_results.json

Method 2: Execution Trace Comparison

Capture and compare execution traces:

Workflow:

1. Instrument code to capture function calls, arguments, and return values
2. Run identical inputs through both versions
3. Compare execution traces for divergences