diff --git a/phpcs.xml b/phpcs.xml
index b457a07..408f309 100644
--- a/phpcs.xml
+++ b/phpcs.xml
@@ -7,6 +7,13 @@
 	<exclude-pattern>/siteimprove/admin/css/*</exclude-pattern>
 	<exclude-pattern>/siteimprove/admin/js/*</exclude-pattern>
 
+	<!-- Test and tooling code. Only /siteimprove is published to WordPress.org,
+	     so WPCS is scoped to the code that actually ships. -->
+	<exclude-pattern>/tests/*</exclude-pattern>
+	<exclude-pattern>/playwright*.config.js</exclude-pattern>
+	<exclude-pattern>/scripts/*</exclude-pattern>
+	<exclude-pattern>/node_modules/*</exclude-pattern>
+
 	<rule ref="WordPress">
 		<exclude name="Squiz.Commenting.FileComment.SpacingAfterComment"/>
 	</rule>