# Frb Develop Feature > Use when adding tests or developing new features in flutter_rust_bridge, when compilation is slow, or when learning twin test naming conventions - Skill: `tomevault-io/frb-develop-feature` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/frb-develop-feature` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/frb-develop-feature/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/frb-develop-feature --- # FRB Develop Feature > **Note:** Check your user-level `remote-testing` rules before running commands. Tests and codegen may require remote execution. ## Overview **Iterate in frb_example/dart_minimal (fast compile), migrate to frb_example/pure_dart (full coverage).** | Phase | Location | Why | |-------|----------|-----| | Iterate | frb_example/dart_minimal | Fast compile = quick feedback | | Migrate | frb_example/pure_dart + pure_dart_pde | Twin tests = automatic coverage of all codegen modes | Write one test → get ~6 variants automatically via TwinNormal suffix. ## When to Use - Adding a new function or feature - Writing tests for new or existing functionality - Compilation feels slow (use frb_example/dart_minimal instead) ## Implementation ```dot digraph workflow { rankdir=TB; node [shape=box]; "Write test + impl in dart_minimal" -> "Run test"; "Run test" -> "Pass?" [shape=diamond]; "Pass?" -> "Move to pure_dart" [label="yes"]; "Pass?" -> "Fix" [label="no"]; "Fix" -> "Run test"; "Move to pure_dart" -> "Add TwinNormal suffix" -> "Run code gen" -> "All tests pass?"; "All tests pass?" -> "Done" [label="yes"]; "All tests pass?" -> "Debug" [label="no"]; "Debug" -> "All tests pass?"; } ``` ### Phase 1: Iterate in frb_example/dart_minimal 1. **Add tests:** - Rust: add function to `frb_example/dart_minimal/rust/src/api/minimal.rs` - Dart: add test to `frb_example/dart_minimal/test/minimal_test.dart` There is usually no need to create any new files. 2. **Add implementations:** Usually need to modify `frb_codegen`, `frb_dart`, and/or `frb_rust`. 3. **Run codegen and test:** ```bash (cd frb_example/dart_minimal && cargo run --manifest-path ../../frb_codegen/Cargo.toml -- generate) ./frb_internal test-dart-native --package frb_example/dart_minimal ``` > **After codegen:** Check your user-level `remote-testing` rules. If codegen was run remotely, pull changes back to local. 4. **Iterate until test passes** ### Phase 2: Migrate to frb_example/pure_dart 1. **Move code to frb_example/pure_dart:** - Rust: `frb_example/pure_dart/rust/src/api/my_feature.rs` - Dart: `frb_example/pure_dart/test/api/my_feature_test.dart` Either add to existing files or create new files. Then remove from frb_example/dart_minimal files. 2. **Add TwinNormal suffix** to all functions and types: | Context | Suffix | Example | |---------|--------|---------| | snake_case | `_twin_normal` | `my_func_twin_normal()` | | PascalCase | `TwinNormal` | `MyStructTwinNormal` | This triggers automatic test generation (~6 variants) under different codegen modes. Always mimic existing frb_example/pure_dart tests for exact patterns. 3. **Run codegen and test:** ```bash # Codegen ./frb_internal precommit-generate # Native tests (can run in parallel) ./frb_internal test-dart-native --package frb_example/pure_dart ./frb_internal test-dart-native --package frb_example/pure_dart_pde # Web tests (optional, for web platform coverage) ./frb_internal test-dart-web --package frb_example/pure_dart ./frb_internal test-dart-web --package frb_example/pure_dart_pde ``` > **After codegen:** Check your user-level `remote-testing` rules. If codegen was run remotely, pull changes back to local. Native tests must pass - they test different codegen configurations. Web tests are optional but recommended for web platform coverage. 4. **Iterate until test passes** You may use frb_example/dart_minimal again if there are bugs and need fast iteration. ## Quick Reference ### Tasks and Commands | Task | Command | |------|---------| | Test dart_minimal | `./frb_internal test-dart-native --package frb_example/dart_minimal` | | Test pure_dart | `./frb_internal test-dart-native --package frb_example/pure_dart` | | Test pure_dart_pde | `./frb_internal test-dart-native --package frb_example/pure_dart_pde` | | Web test pure_dart | `./frb_internal test-dart-web --package frb_example/pure_dart` | | Web test pure_dart_pde | `./frb_internal test-dart-web --package frb_example/pure_dart_pde` | | Code generation | `./frb_internal precommit-generate` | ### Architecture - **Doc:** `website/docs/guides/contributing/overview.md` - System architecture, codegen flow, directory structure - **Key directories:** | Directory | Purpose | |-----------|---------| | `frb_codegen/` | Code generator (IR → Rust/Dart output) | | `frb_dart/` | Dart runtime library | | `frb_rust/` | Rust runtime library | | `frb_example/` | Examples + tests (`pure_dart` has most coverage) | ## Common Mistakes | Mistake | Fix | |---------|-----| | Skipping frb_example/dart_minimal phase | Start there - saves time on compilation | | Forgetting TwinNormal suffix | Add before code gen in frb_example/pure_dart | | Moving test without updating imports | Check import paths after migration | | Not running code gen after move | Always run `./frb_internal precommit-generate` | ## Related Skills - `frb-code-generation` - Which generation commands to run - `frb-test` - How to run tests locally - `frb-debugging` - Debug code generation issues - `frb-prepare-pr` - Preparing a PR for review --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/fzyzcjy) — claim your Tome and manage your conversions.