Pattern 4: Resource Cleanup

Context

Your tests allocate resources – files, network ports, containers, telemetry backends – that must be released even when assertions fail.

Problem

Forgetting to release resources causes nondeterministic failures, leaking containers, or state pollution between tests. Manual cleanup logic scatters across tests and is easy to miss.

Solution

Use Chicago TDD Tools fixtures and the RAII guarantees they provide. Wrap resource management inside fixture_test! or fixture_test_with_timeout!, storing handles in the fixture. Allow Drop implementations and the framework cleanup to run automatically so every test returns to a known good state.

Forces

• Determinism vs. speed: automated teardown must be reliable without slowing the hot path
• Simplicity vs. observability: cleanup should be invisible unless a failure occurs
• Isolation vs. reuse: fixtures create fresh state while sharing setup logic

Examples

#![allow(unused)]
fn main() {
use chicago_tdd_tools::prelude::*;
use testcontainers::clients::Cli as DockerCli;

struct DockerFixture {
    docker: DockerCli,
}

fixture_test!(test_exec_container_command, fixture, {
    // Arrange
    let docker = DockerCli::default();
    let container = docker.run("alpine:3.19");

    // Act
    let result = container.exec("echo", &["ok"])?;

    // Assert
    assert_eq!(result.stdout, "ok\n");

    Ok::<(), testcontainers::Error>(())
});
}

The fixture ensures containers stop even if the assertion fails.

Related Patterns

• Pattern 5: Real Collaborators
• Pattern 16: Fixture Lifecycle Management
• Pattern 18: Timeout Defense in Depth