tmuxido/CLAUDE.md

Rust Project — Claude Instructions

Mandatory Rules

1. Always write tests alongside production code — no feature ships without tests
2. Always verify tests pass after every change — the PostToolUse hook runs automatically; if it shows failures, fix them before moving on
3. Run cargo clippy -- -D warnings and resolve all warnings
4. Run cargo fmt before considering any task complete

Available MCP Tools

Install with curl -sSf https://raw.githubusercontent.com/USUARIO/claude-rust-scaffold/main/install.sh | sh

Server	Tools	Purpose
rust-mcp	cargo_check, cargo_build, cargo_test, cargo_clippy, cargo_fmt, cargo_add	Run cargo commands directly
crates	search, versions, dependencies, docs	Explore crates.io and docs.rs

Test Structure

Unit Tests — inside src/

Place at the bottom of each source file:

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn should_return_error_when_input_is_empty() {
        // arrange
        let input = "";
        // act
        let result = parse(input);
        // assert
        assert!(result.is_err());
    }
}

• Name tests descriptively: should_<outcome>_when_<condition>
• Cover: happy path, edge cases (empty, max values), error cases

Integration Tests — tests/ directory

• One file per feature or behavior
• Use only public interfaces (pub)
• Simulate real usage end-to-end

// tests/parsing.rs
use tmuxido::parse;

#[test]
fn parses_valid_input_successfully() {
    let result = parse("valid input");
    assert!(result.is_ok());
}

Snapshot Testing with insta

For complex outputs or large structs:

#[test]
fn renders_report_correctly() {
    let report = generate_report(&data);
    insta::assert_snapshot!(report);
}

Review snapshots: cargo insta review

Property Testing with proptest

For pure functions over wide input domains:

use proptest::prelude::*;

proptest! {
    #[test]
    fn round_trip_encode_decode(s in ".*") {
        let encoded = encode(&s);
        prop_assert_eq!(decode(&encoded), s);
    }
}

Recommended Cargo.toml dev-dependencies

[dev-dependencies]
proptest = "1"
insta = { version = "1", features = ["json", "yaml"] }
mockall = "0.13"

# if async:
tokio = { version = "1", features = ["full", "test-util"] }

Recommended Project Structure

tmuxido/
├── Cargo.toml
├── src/
│   ├── lib.rs          # core logic (unit tests at bottom)
│   ├── main.rs         # entrypoint (thin, delegates to lib)
│   └── module/
│       └── mod.rs      # #[cfg(test)] mod tests {} at bottom
├── tests/
│   └── integration.rs  # integration tests
└── benches/
    └── bench.rs        # benchmarks (optional)

Prefer lib.rs + main.rs split so logic stays testable independently of the binary entrypoint.