Pattern 16: Fixture Lifecycle Management

Context

Complex tests require deterministic setup and teardown of shared state: databases, telemetry, temporary directories.

Problem

Manual lifecycle logic is error-prone. Forgetting teardown causes cascading failures across tests. Async setup complicates matters further.

Solution

Wrap lifecycle responsibilities in TestFixture or AsyncFixtureManager. Use the fixture to hold handles and expose helper methods. Let Drop and the manager .teardown() guarantee cleanup. For async resources, implement AsyncFixtureProvider and return strongly typed handles.

Forces

• Determinism vs. flexibility: fixtures must isolate state yet allow custom behavior per test
• Async vs. sync complexity: asynchronous resources require explicit lifecycle boundaries
• Performance vs. safety: reuse is tempting, but fresh fixtures avoid hidden coupling

Examples

#![allow(unused)]
fn main() {
struct DbProvider;

impl chicago_tdd_tools::core::async_fixture::private::Sealed for DbProvider {}

impl AsyncFixtureProvider for DbProvider {
    type Fixture<'a> = DatabaseHandle;
    type Error = DbError;

    fn create_fixture<'a>(&'a self) -> DbFuture<'a, DatabaseHandle> {
        Box::pin(async move { DatabaseHandle::connect().await })
    }
}

async_test!(test_query_latency, {
    let manager = AsyncFixtureManager::new(DbProvider);
    let handle = manager.setup().await?;
    // ...
    manager.teardown().await?;
    Ok(())
});
}

Related Patterns

• Pattern 4: Resource Cleanup
• Pattern 12: Type Safety with GATs
• Pattern 18: Timeout Defense in Depth