Continuous Integration

Continuous Integration (CI) automates formatting checks, static analysis, unit and integration tests, documentation verification, and security audits on every pull request and commit. A well-structured Rust CI pipeline fails fast on any regression while caching Cargo's registry and incremental build artifacts.

Production Rust CI Pipeline Stages:

  [ Stage 1: Fast Static Gates (<30s) ]
    ├── `cargo fmt --all -- --check`
    └── `cargo deny check` / `cargo audit`
              |
              v
  [ Stage 2: Lint & Documentation Verification ]
    ├── `cargo clippy --workspace --all-targets --all-features --locked -- -D warnings`
    └── `RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps --all-features --locked`
              |
              v
  [ Stage 3: Multi-OS & MSRV Test Matrix ]
    ├── `cargo test --workspace --all-targets --all-features --locked` (Linux, macOS, Windows)
    ├── `cargo test --workspace --doc --all-features --locked`
    └── MSRV Check (`toolchain: "1.85.0"`)

Complete GitHub Actions Workflow for a Rust Workspace

Below is a production-ready .github/workflows/ci.yml configuration incorporating --locked verification, zero-warning gates, and multi-platform matrix testing:

name: CI

on:
  push:
    branches: [main]
  pull_request:

env:
  CARGO_TERM_COLOR: always
  RUSTFLAGS: "-D warnings"
  RUSTDOCFLAGS: "-D warnings"

jobs:
  fmt:
    name: Rustfmt
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@stable
        with:
          components: rustfmt
      - run: cargo fmt --all -- --check

  clippy-and-docs:
    name: Clippy & Docs
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@stable
        with:
          components: clippy
      - uses: Swatinem/rust-cache@v2
      - run: cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
      - run: cargo doc --workspace --no-deps --all-features --locked

  test:
    name: Test Suite (${{ matrix.os }})
    runs-on: ${{ matrix.os }}
    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@stable
      - uses: Swatinem/rust-cache@v2
      - run: cargo test --workspace --all-targets --all-features --locked
      - run: cargo test --workspace --doc --all-features --locked

Measuring Source-Based Code Coverage (cargo-llvm-cov)

Rust's compiler includes native LLVM source-based code coverage instrumentation (-C instrument-coverage), which tracks exact expression and branch execution counts without the inaccuracies of DWARF line-table sampling. The ecosystem tool cargo-llvm-cov (cargo install cargo-llvm-cov --locked) wraps this compiler pass into a single command:

# 1. Install the llvm-tools-preview component and cargo-llvm-cov:
rustup component add llvm-tools-preview
cargo install cargo-llvm-cov --locked

# 2. Run tests and generate an HTML coverage report in target/llvm-cov/html/:
cargo llvm-cov --all-features --workspace --html

# 3. Export an LCOV report for CI coverage badges or enforce a minimum threshold:
cargo llvm-cov --all-features --workspace --fail-under-lines 85

pub fn classify_status(code: u16) -> &'static str {
    match code {
        200..=299 => "success",
        300..=399 => "redirect",
        400..=499 => "client_error",
        500..=599 => "server_error",
        _ => "unknown",
    }
}

fn main() {
    assert_eq!(classify_status(200), "success");
    assert_eq!(classify_status(404), "client_error");
    assert_eq!(classify_status(503), "server_error");
    println!("CI status checks passed");
}

CI status checks passed