diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 87e1f7ec86..a39deb5974 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -105,6 +105,14 @@ When making changes to the compiler source code, the most helpful test step to
 run is `test-behavior`. When editing documentation it is `docs`. You can find
 this information and more in the `--help` menu.
 
+#### Testing Changes to std lib
+
+To quickly test a change to a file in the standard library, you can run zig test and specify a custom lib directory with the follow command-line argument.
+
+```bash
+./build/zig test lib/std/fmt.zig --zig-lib-dir lib --main-pkg-path lib/std
+```
+
 #### Testing Non-Native Architectures with QEMU
 
 The Linux CI server additionally has qemu installed and sets `-Denable-qemu`.