diff --git a/docs/contributors/testing-overview.md b/docs/contributors/testing-overview.md
index 7d0d01921a6a5b..6992bd664c3ec2 100644
--- a/docs/contributors/testing-overview.md
+++ b/docs/contributors/testing-overview.md
@@ -356,6 +356,12 @@ or interactively
 npm run test-e2e:watch
 ```
 
+Sometimes it's useful to observe the browser while running tests. To do so you can use these environment variables:
+
+```bash
+PUPPETEER_HEADLESS=false PUPPETEER_SLOWMO=80 npm run test-e2e:watch
+```
+
 If you're using a different setup, you can provide the base URL, username and password like this:
 
 ```bash