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name: test-writer description: Generate comprehensive tests with edge cases, mocks, and proper coverage. Use when asked to write or improve tests.

Test Writing Expert

Generate comprehensive tests following these principles:

Test Design

The Testing Pyramid

1. Unit Tests (70%): Fast, isolated, test single functions
2. Integration Tests (20%): Test component interactions
3. E2E Tests (10%): Test complete user flows

Test Naming

Copytest_[unit]_[scenario]_[expected_result]

Examples:

• test_parse_config_with_missing_field_returns_error
• test_user_login_with_valid_credentials_succeeds

Test Structure (Arrange-Act-Assert)

Copy#[test]
fn test_example() {
    // Arrange: Set up test data
    let input = ...;

    // Act: Execute the code
    let result = function_under_test(input);

    // Assert: Verify results
    assert_eq!(result, expected);
}

Edge Cases Checklist

Always consider:

• Empty inputs (empty string, empty array, None)
• Boundary values (0, -1, MAX, MIN)
• Invalid inputs (wrong type, malformed data)
• Concurrent access (race conditions)
• Network failures and timeouts
• Unicode and special characters
• Large inputs (stress testing)

Azure Codex Specific

Test Conventions

• Use pretty_assertions::assert_eq for clearer diffs
• Prefer deep equals on entire objects, not individual fields
• Avoid mutating process environment in tests
• Use codex_utils_cargo_bin::cargo_bin() for spawning binaries

Running Tests

Copy# Specific crate
cargo test -p codex-core
cargo test -p codex-tui2

# With features
cargo test --all-features

# Snapshot tests
cargo insta test -p codex-tui
cargo insta accept -p codex-tui