---
description: 'Guidelines for building C++ Arduino applications'
applyTo: '**/*.cpp, **/*.h, **/*.hpp, **/*ino'
---

# C++ Development

## C++ Instructions
- C++ standard for Arduino.
- Write clear and concise comments for each function.

## General Instructions
- Make only high confidence suggestions when reviewing code changes.
- Write code with good maintainability practices, including comments on why certain design decisions were made.
- Handle edge cases and write clear exception handling.
- For libraries or external dependencies, mention their usage and purpose in comments.
- Arduino does not support standard libray
- Standard library can be used in the unit tests

## Formatting

- Apply code-formatting style defined in `.clang-format`.
- Prefer file-scoped namespace declarations and single-line using directives.
- Insert a newline before the opening curly brace of any code block (e.g., after `if`, `for`, `while`, `foreach`, `using`, `try`, etc.).
- Ensure that the final return statement of a method is on its own line.
- Use pattern matching and switch expressions wherever possible.
- Use `nameof` instead of string literals when referring to member names.
- Ensure that XML doc comments are created for any public APIs. When applicable, include `<example>` and `<code>` documentation in the comments.

## Project Setup and Structure

- Explain the purpose of each generated file and folder to build understanding of the project structure.
- Demonstrate how to organize code using feature folders or domain-driven design principles.
- Show proper separation of concerns with models, services, and data access layers.
- Explain the Program.cpp and configuration system in C++ including environment-specific settings.

## Testing

- Always include test cases for critical paths of the application.
- Guide users through creating unit tests.
- Do not emit "Act", "Arrange" or "Assert" comments.
- Copy existing style in nearby files for test method names and capitalization.
- Explain integration testing approaches for API endpoints.
- Demonstrate how to mock dependencies for effective testing.
- Show how to test authentication and authorization logic.
- Explain test-driven development principles as applied to API development.

## Performance Optimization

- Guide users on implementing caching strategies (in-memory, distributed, response caching).
- Explain asynchronous programming patterns and why they matter for API performance.
- Demonstrate pagination, filtering, and sorting for large data sets.
- Show how to implement compression and other performance optimizations.
- Explain how to measure and benchmark API performance.