diff --git a/HACKING.md b/HACKING.md
index 4922eb195..54cc4ebd1 100644
--- a/HACKING.md
+++ b/HACKING.md
@@ -213,10 +213,11 @@ Buster (or later).
 ```bash
 host$ pip3 install splinter
 host$ pip3 install pytest-splinter
+host$ pip3 install pytest-xdist  # optional, to run tests in parallel
+host$ sudo apt install firefox
 host$ sudo apt install python3-pytest-bdd
 host$ sudo apt install xvfb python3-pytest-xvfb  # optional, to avoid opening browser windows
-host$ sudo apt install firefox
-host$ sudo apt install smbclient # optional, to test samba
+host$ sudo apt install smbclient  # optional, to test samba
 ```
 
 - Install the latest version of geckodriver. It is usually a single binary which
@@ -275,6 +276,13 @@ If xvfb is installed and you still want to see browser windows, use the
 vm$ py.test-3 --no-xvfb -m mediawiki --include-functional
 ```
 
+Tests can also be run in parallel, provided you have the pytest-xdist plugin
+installed.
+
+```
+$ py.test-3 -n 4 --dist=loadfile --include-functional -m essential
+```
+
 ## Building the Documentation Separately
 
 FreedomBox Service (Plinth) man page is built from DocBook source in the `doc/`