diff --git a/src/rules/no-event-shorthand.js b/src/rules/no-event-shorthand.js
index 635fa5d6..b01e4b61 100644
--- a/src/rules/no-event-shorthand.js
+++ b/src/rules/no-event-shorthand.js
@@ -44,8 +44,9 @@ const rule = utils.createCollectionMethodRule(
 		'mousemove',
 		'mouseout',
 		'mouseover',
-		'mouseup'
-	].concat( ajaxEvents ),
+		'mouseup',
+		...ajaxEvents
+	],
 	( node ) => node === true ?
 		'Use the `allowAjaxEvents` option to allow `ajax*` methods. Prefer `.on` or `.trigger`' :
 		`Prefer .on or .trigger to .${ node.callee.property.name }`,
diff --git a/test-self/.eslintrc.json b/test-self/.eslintrc.json
index e8463e30..1e431483 100644
--- a/test-self/.eslintrc.json
+++ b/test-self/.eslintrc.json
@@ -1,6 +1,6 @@
 {
 	"root": true,
-	"extends": "wikimedia/client-es5",
+	"extends": "wikimedia/client",
 	"plugins": [ "self" ],
 	"globals": {
 		"$": "readonly"
diff --git a/test-self/all/constructor.js b/test-self/all/constructor.js
index 26d917b1..85589a29 100644
--- a/test-self/all/constructor.js
+++ b/test-self/all/constructor.js
@@ -1,5 +1,5 @@
 // eslint-disable-next-line self/no-jquery-constructor
-$( function () {} );
+$( () => {} );
 
 // eslint-disable-next-line self/no-jquery-constructor
 $( '.selector' );
diff --git a/test-self/deprecated-1.8/test.js b/test-self/deprecated-1.8/test.js
index bdc3f2d1..4a5c3918 100644
--- a/test-self/deprecated-1.8/test.js
+++ b/test-self/deprecated-1.8/test.js
@@ -27,16 +27,16 @@ $x.andSelf();
 $x.error( fn );
 
 // eslint-disable-next-line self/no-load-shorthand
-$x.load( function () {} );
+$x.load( () => {} );
 
 // eslint-disable-next-line self/no-on-ready
-$( document ).on( 'ready', function () {} );
+$( document ).on( 'ready', () => {} );
 
 // eslint-disable-next-line self/no-size
 $x.size();
 
 // eslint-disable-next-line self/no-unload-shorthand
-$x.unload( function () {} );
+$x.unload( () => {} );
 
 /* 1.7 */
 // eslint-disable-next-line self/no-live
diff --git a/test-self/recommended/test.js b/test-self/recommended/test.js
index 0093745b..9f927bde 100644
--- a/test-self/recommended/test.js
+++ b/test-self/recommended/test.js
@@ -1,2 +1,2 @@
 // eslint-disable-next-line self/variable-pattern
-var foo = $( '.foo' );
+const foo = $( '.foo' );
diff --git a/test-self/slim/test.js b/test-self/slim/test.js
index 32c8c38d..819ca723 100644
--- a/test-self/slim/test.js
+++ b/test-self/slim/test.js
@@ -12,7 +12,7 @@ $x.slideDown();
 // eslint-disable-next-line self/no-ajax
 $.get( 'url' );
 // eslint-disable-next-line self/no-ajax-events
-$x.on( 'ajaxComplete', function () {} );
+$x.on( 'ajaxComplete', () => {} );
 // eslint-disable-next-line self/no-load
 $x.load();
 // eslint-disable-next-line self/no-parse-xml
diff --git a/tests/rules/no-event-shorthand.js b/tests/rules/no-event-shorthand.js
index 935d5263..9866f7b4 100644
--- a/tests/rules/no-event-shorthand.js
+++ b/tests/rules/no-event-shorthand.js
@@ -41,14 +41,15 @@ const forbidden = [
 	'mousemove',
 	'mouseout',
 	'mouseover',
-	'mouseup'
-].concat( ajaxEvents );
-let valid = [];
-let invalid = [];
+	'mouseup',
+	...ajaxEvents
+];
+const valid = [];
+const invalid = [];
 
 forbidden.forEach( ( method ) => {
 	const error = 'Prefer .on or .trigger to .' + method;
-	valid = valid.concat(
+	valid.push(
 		{
 			code: method + '()',
 			docgen: false
@@ -76,7 +77,7 @@ forbidden.forEach( ( method ) => {
 			docgen: false
 		}
 	);
-	invalid = invalid.concat(
+	invalid.push(
 		{
 			code: '$("div").' + method + '(handler)',
 			errors: [ error ],
@@ -107,19 +108,19 @@ forbidden.forEach( ( method ) => {
 		}
 	);
 } );
+valid.push(
+	// Don't conflict with Ajax load
+	'$div.load( "url", handler )',
+	...ajaxEvents.map( ( eventName ) => ( {
+		code: '$div.' + eventName + '()',
+		options: [ { allowAjaxEvents: true } ]
+	} ) ),
+	...ajaxEvents.map( ( eventName ) => ( {
+		code: '$div.on("' + eventName + '", fn)',
+		options: [ { allowAjaxEvents: true } ]
+	} ) )
+);
 ruleTester.run( 'no-event-shorthand', rule, {
-	valid: valid.concat( [
-		// Don't conflict with Ajax load
-		'$div.load( "url", handler )'
-	] ).concat(
-		ajaxEvents.map( ( eventName ) => ( {
-			code: '$div.' + eventName + '()',
-			options: [ { allowAjaxEvents: true } ]
-		} ) ),
-		ajaxEvents.map( ( eventName ) => ( {
-			code: '$div.on("' + eventName + '", fn)',
-			options: [ { allowAjaxEvents: true } ]
-		} ) )
-	),
+	valid,
 	invalid
 } );
diff --git a/tests/rules/no-load-shorthand.js b/tests/rules/no-load-shorthand.js
index 0cba14a4..6718b752 100644
--- a/tests/rules/no-load-shorthand.js
+++ b/tests/rules/no-load-shorthand.js
@@ -5,9 +5,7 @@ const RuleTester = require( '../../tools/rule-tester' );
 
 const error = 'Prefer .on or .trigger to .load';
 
-const ruleTester = new RuleTester( {
-	parserOptions: { ecmaVersion: 2015 }
-} );
+const ruleTester = new RuleTester();
 ruleTester.run( 'no-load-shorthand', rule, {
 	valid: [
 		'load()',
diff --git a/tests/rules/no-ready.js b/tests/rules/no-ready.js
index 0fa00b13..50a3e2c8 100644
--- a/tests/rules/no-ready.js
+++ b/tests/rules/no-ready.js
@@ -5,9 +5,7 @@ const RuleTester = require( '../../tools/rule-tester' );
 
 const error = '.ready is not allowed';
 
-const ruleTester = new RuleTester( {
-	parserOptions: { ecmaVersion: 2015 }
-} );
+const ruleTester = new RuleTester();
 ruleTester.run( 'no-ready', rule, {
 	valid: [
 		'ready(function() { })',
diff --git a/tests/rules/variable-pattern.js b/tests/rules/variable-pattern.js
index bf658429..f33c4249 100644
--- a/tests/rules/variable-pattern.js
+++ b/tests/rules/variable-pattern.js
@@ -14,12 +14,10 @@ ruleTester.run( 'variable-pattern', rule, {
 		'var $div = $("<div>")',
 		{
 			code: 'let $letDiv = $("<div>")',
-			parserOptions: { ecmaVersion: 2015 },
 			docgen: false
 		},
 		{
 			code: 'const $constDiv = $("<div>")',
-			parserOptions: { ecmaVersion: 2015 },
 			docgen: false
 		},
 		{
@@ -168,13 +166,11 @@ ruleTester.run( 'variable-pattern', rule, {
 		},
 		{
 			code: 'let letDiv = $("<div>")',
-			parserOptions: { ecmaVersion: 2015 },
 			docgen: false,
 			errors: [ error ]
 		},
 		{
 			code: 'const constDiv = $("<div>")',
-			parserOptions: { ecmaVersion: 2015 },
 			docgen: false,
 			errors: [ error ]
 		},
diff --git a/tools/rule-tester.js b/tools/rule-tester.js
index 2730ca60..03bf546d 100644
--- a/tools/rule-tester.js
+++ b/tools/rule-tester.js
@@ -1,4 +1,9 @@
 'use strict';
 
-// TODO: This no longer overrides RuleTester so can be deleted and replaced
-module.exports = require( 'eslint-docgen' ).RuleTester;
+const RuleTester = require( 'eslint-docgen' ).RuleTester;
+
+RuleTester.setDefaultConfig( {
+	parserOptions: { ecmaVersion: 2015 }
+} );
+
+module.exports = RuleTester;