Testing and tools

Finding concurrency bugs on purpose: race detectors, deterministic schedulers, stress runs, model checkers, and the tools that show what every thread is waiting for.

All categories · How they connect

• Race detector — A tool that instruments memory accesses as the program runs and reports the data races that actually happened in that run — ThreadSanitizer, Go's -race.
• Deterministic scheduling for tests — Running concurrent code under a controlled scheduler or a fake clock, so that an interleaving or a timeout can be reproduced on demand — Rust's loom, Go's testing/synctest.
• Stress testing — Running concurrent code many times, under load and with many threads, so that rare interleavings get a chance to show up.
• Model checking — Exploring every state and interleaving of a model of a program — in TLA+, SPIN, or loom — to prove a property or produce a counterexample.
• Debugging concurrent programs — Thread dumps, deadlock detectors and tracing that show what every thread or task is waiting for at a given moment.
• Profiling concurrent programs — Measuring where the time goes when many threads run — waiting for locks, waiting to be scheduled, and bouncing cache lines — and not only which functions are hot.