https://mvega.dev/tags/concurrency/Recent content in Concurrency on Moises VegaHugoen-usMoises VegaSun, 16 Aug 2026 00:00:00 +0000https://mvega.dev/posts/synctest-concurrent-testing/Sun, 16 Aug 2026 00:00:00 +0000https://mvega.dev/posts/synctest-concurrent-testing/<p>Notes from Alexander Baygeldin&rsquo;s GopherCon 2026 talk, &ldquo;(Sync)testing Concurrent Code with Confidence.&rdquo;</p> <p>Testing concurrent code used to mean picking one of three bad options: hacky (poke at internals), flaky (<code>time.Sleep(100 * time.Millisecond)</code> and hope), or slow (sleep long enough that it&rsquo;s reliable). <code>testing/synctest</code> removes the tradeoff by giving the test a fake clock.</p> <h2 id="the-fake-clock">The fake clock</h2> <p>Inside <code>synctest.Test</code>, time doesn&rsquo;t pass on its own. It jumps forward only when every goroutine in the bubble is blocked. A one-hour timeout resolves instantly and deterministically.</p>