Rust Testing Advanced — Integration Tests, Benchmarks, Property-Based Testing, and Mocking

[dev-dependencies]
criterion = "0.5"
proptest = "1.0"
mockall = "0.11"

[[bench]]
name = "my_bench"
harness = false

// Integration test in tests/api_test.rs
use myapp;

#[test]
fn test_create_user() {
    // Tests the public API through its interface
    let result = myapp::create_user("alice@test.com");
    assert!(result.is_ok());
}

// Benchmark
use criterion::{black_box, criterion_group, criterion_main, Criterion};

fn fibonacci(n: u64) -> u64 {
    match n { 0 => 0, 1 => 1, _ => fibonacci(n-1) + fibonacci(n-2) }
}

fn bench_fib(c: &mut Criterion) {
    c.bench_function("fib 20", |b| b.iter(|| fibonacci(black_box(20))));
}

criterion_group!(benches, bench_fib);
criterion_main!(benches);

// Property-based testing
proptest! {
    #[test]
    fn test_reverse_roundtrip(s: String) {
        let reversed: String = s.chars().rev().collect();
        let double_reversed: String = reversed.chars().rev().collect();
        assert_eq!(s, double_reversed);
    }
}