Go 1.25 introduced testing/synctest, a package that brings deterministic scheduling and control over concurrency during tests. For developers who struggle with flaky tests, hidden data races, or hard-to-reproduce timing issues, synctest offers a powerful solution: it lets you run concurrent code in a bubble, so you can efficiently explore interleavings, force edge cases, and prove correctness.

In this talk, we’ll explore the motivation behind synctest, and dive into the testing patterns it enables. We’ll walk through practical examples of converting existing tests to use synctest. The session includes a demo illustrating how synctest can turn an intermittently failing test into a deterministic one, and surface bugs that traditional tests might miss.

Whether you build concurrent systems, maintain production Go services, or simply want more reliable tests, this talk will give you a solid understanding of what synctest brings to Go—and how you can start using it today.