Contract-Based Porting: Cross-Language Feature Parity via TDD

When to Use

• Porting native Android (Kotlin/Java) or iOS (Swift/ObjC) features to Flutter (Dart)
• Ensuring a Flutter app has 100% feature parity with a reference native implementation
• Any cross-language porting task where you need guaranteed completeness
• Migrating from one framework to another (e.g., React→Vue, Express→FastAPI)

Core Principle

Never port line-by-line. Port contract-by-contract.

The #1 failure mode in cross-language porting is missing features — not bugs. The fix is to extract the entire public API surface before writing a single line of target code.

3-Step Methodology

Step 1: Extract the Single Source of Truth (SSOT)