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name: chicago-tdd-pattern description: "Master Chicago TDD (state-based testing). Verify observable behavior with real collaborators using AAA pattern." allowed_tools: "Read, Write, Bash(cargo make test:*)"

Chicago TDD Pattern

Core Philosophy

Chicago TDD = State-based testing with real collaborators

Verify observable behavior changes (return values, state mutations, side effects), NOT internal implementation or mocks.

AAA Pattern

Copy#[test]
fn test_feature() {
    // ARRANGE: Set up real objects (no mocks)
    let manager = Manager::new(temp_dir.path());

    // ACT: Call the public API
    manager.execute("command").unwrap();

    // ASSERT: Verify observable state
    assert_eq!(manager.status(), Status::Complete);
}

Key Principles

• Use real objects (not mocks)
• Test observable behavior
• Avoid testing internal implementation
• One assertion = one test (focused)
• No flaky tests (deterministic)

Reference

See CLAUDE.md sections:

• Development Workflow (Chicago TDD)
• Stack: chicago-tdd-tools 1.4.0
• Agents: test-engineer