composable-rust-testing

Write unit tests for Rust reducers by using a ReducerTest builder within in-file #[cfg(test)] modules to exercise pure state transitions deterministically. This approach isolates reducer logic from I/O dependencies, enabling fast and reliable state transition verification.

Set up Rust integration tests with real dependencies by spinning up real components like PostgreSQL and message buses via testcontainers, running migrations, and validating end-to-end behavior in a realistic environment. This ensures reliable integration testing without manual infrastructure management.

Property-based testing with proptest in Rust applications works by automatically generating varied test inputs to uncover edge cases in state transitions and reducer logic. It validates that defined properties hold across a wide range of inputs, revealing edge cases that manual test cases might miss.

Yes, you can use TestStore and FixedClock to deterministically drive and verify async workflows in Rust. These test utilities, combined with saga-wait patterns and mocks, allow you to control time and state, ensuring deterministic outcomes in asynchronous tests.

Organize tests across multiple crates in a Composable Rust project by enforcing best practices for test organization, separating fast unit tests for reducers from integration tests, and leveraging shared test utilities like TestStore and mocks to maintain consistency.

Use testcontainers instead of mocks for Rust integration testing when you need end-to-end validation with real dependencies like PostgreSQL and message buses. Mocks are better for isolating specific components, while testcontainers provide realistic environments for comprehensive integration tests.