Delightful integration tests in Rust

Summary

Delightful integration tests in Rust When I first learned about testing in Rust I was surprised by the lack of what I consider a basic feature: test setup and teardown. Many other popular testing frameworks have it: jest, pytest fixtures, and so on. Global setup and teardown are especially useful in integration tests. In integration tests, as well as in similar component tests or end-to-end tests, the code runs against a complete or partial set of the application infrastructure. In this important class of tests we don't mock out database access or skip message brokers. Setup and teardown are good candidates for provisioning that infrastructure so we can reuse it across multiple tests. But alas, Rust does not provide built-in setup and teardown, and what's more, by default all tests run concurrently on different threads, so creating and reusing global state is a bit clunky. Seems that writing integration tests in Rust is a miserable experience. Or is it? Despite my initial skepticism I now think that integration tests in Rust are actually a delight. The delightful Rust concept i'm refering to is RAII, and the crate I now reach for is testcontainers-rs. The core idea is simple: make Docker container creation easy and ergonomic, and clean containers up automatically. This idea, leveraging RAII for automatic cleanup, removes the need for global setup and teardown and paves a direct path to completely isolated tests that can comfortably run in parallel. Resource Acquisition Is Infrastructure Rust heavily uses the RAII (Resource Acquisition Is Initialization) pattern. RAII's main goal is to automatically clean up memory and resources, removing the need for manual management in many common use cases. This useful pattern can be exploited a bit, and extended to automatically manage out-of-process resources. In our use case we wish to make a Docker container a resource and use Rust's ownership rules and Drop trait to clean it up automatically. To demonstrate RAII relevance, i...