<skill_overview> <purpose>Write fast, reliable, and maintainable Rust tests</purpose> <triggers> <trigger>Writing unit tests</trigger> <trigger>Adding integration tests</trigger> <trigger>Testing async code</trigger> <trigger>Improving test reliability</trigger> </triggers> <sources> <source url="https://doc.rust-lang.org/book/ch11-00-testing.html">The Rust Book - Testing</source> </sources> </skill_overview> <test_structure> <rules> <rule>Use #[cfg(test)] mod tests in the same module for unit tests</rule> <rule>Put integration tests in tests/ as separate crates</rule> <rule>Keep tests independent and deterministic</rule> </rules> </test_structure> <arrange_act_assert> <rule>Structure each test with Arrange, Act, Assert</rule> <example> <code> #[test] fn add_two_numbers_returns_sum() { let result = add(2, 3); assert_eq!(5, result); } </code> </example> </arrange_act_assert> <async_tests> <rules> <rule>Use an async test harness provided by your runtime</rule> <rule>Avoid sleeps; use timeouts and deterministic inputs</rule> </rules> </async_tests> <assertions> <rules> <rule>Use assert!, assert_eq!, assert_ne! for clarity</rule> <rule>Use matches! for enum pattern assertions</rule> </rules> </assertions> <anti_patterns> <avoid name="order_dependent">Tests that depend on execution order</avoid> <avoid name="real_external">Hitting real external services in unit tests</avoid> <avoid name="global_mutable">Global mutable state shared across tests</avoid> </anti_patterns>