doc: Updates to TESTING tricks

test-playwright/TESTING.md

@@ -65,7 +65,23 @@ This corresponds to: `did:ethr:0x0000694B58C2cC69658993A90D3840C560f2F51F`
 
 ## Data Reset Instructions
 
-[Rewrite to use custom data directories for each browser]
+### Chromium
+
+```bash
+ rm -rf profiles/dev2 && \ 
+ mkdir -p profiles/dev2 && \
+ chromium --user-data-dir=profiles/dev2 --start-maximized --auto-open-devtools-for-tabs http://localhost:8080
+```
+
+### Firefox
+
+Here is the equivalent command for **Firefox** using a custom profile and opening a local page:
+
+```bash
+rm -rf profiles/dev2 && \
+mkdir -p profiles/dev2 && \
+firefox --no-remote --profile $(realpath profiles/dev2) --devtools --new-window http://localhost:8080
+```
 
 ## Troubleshooting