diff --git a/doc/scripts/header.js b/doc/scripts/header.js
index d31b912..f8d1e33 100644
--- a/doc/scripts/header.js
+++ b/doc/scripts/header.js
@@ -1,34 +1,30 @@
-var domReady = function(callback) {
-	var state = document.readyState ;
-    if ( state === 'interactive' || state === 'complete' ) {
-		callback() ;
-	}
-	else {
+const domReady = function (callback) {
+	const state = document.readyState;
+	if (state === 'interactive' || state === 'complete') {
+		callback();
+	} else {
 		document.addEventListener('DOMContentLoaded', callback);
 	}
-} ;
-
+};
 
-domReady(function(){
-
-	var projectname = document.createElement('a');
+domReady(function () {
+	const projectname = document.createElement('a');
 	projectname.classList.add('project-name');
 	projectname.text = 'union-find/contiguous';
-	projectname.href = './index.html' ;
+	projectname.href = './index.html';
 
-	var header = document.getElementsByTagName('header')[0] ;
-	header.insertBefore(projectname,header.firstChild);
+	const header = document.querySelectorAll('header')[0];
+	header.insertBefore(projectname, header.firstChild);
 
-	var testlink = document.querySelector('header > a[data-ice="testLink"]') ;
-	testlink.href = 'https://coveralls.io/github/union-find/contiguous' ;
-	testlink.target = '_BLANK' ;
+	const testlink = document.querySelector('header > a[data-ice="testLink"]');
+	testlink.href = 'https://coveralls.io/github/union-find/contiguous';
+	testlink.target = '_BLANK';
 
-	var searchBox = document.querySelector('.search-box');
-	var input = document.querySelector('.search-input');
+	const searchBox = document.querySelector('.search-box');
+	const input = document.querySelector('.search-input');
 
-	// active search box when focus on searchBox.
-	input.addEventListener('focus', function(){
+	// Active search box when focus on searchBox.
+	input.addEventListener('focus', function () {
 		searchBox.classList.add('active');
 	});
-
 });
diff --git a/src/adt/Forest.js b/src/adt/Forest.js
index f74576a..3276751 100644
--- a/src/adt/Forest.js
+++ b/src/adt/Forest.js
@@ -1,35 +1,25 @@
-import { selfs } from '../fundamentals/index.js' ;
+import {identity} from '../fundamentals/index.js';
 
-export function union ( p , a , b ) {
+export const union = (p, a, b) => {
+	p[find(p, b)] = find(p, a);
 
-	p[ find( p , b ) ] = find( p , a ) ;
+	return a;
+};
 
-	return a ;
+export const find = (p, x) => {
+	while (x !== p[x]) x = p[x];
 
-}
-
-export function find ( p , x ) {
-
-	while ( x !== p[x] ) x = p[x] ;
-
-	return x ;
+	return x;
+};
 
+export function Universe(n, List = Array) {
+	this.p = identity(n, List);
 }
 
-export function Universe ( n , List = Array ) {
-	this.p = selfs( n , List ) ;
-}
-
-Universe.prototype.union = function ( a , b ) {
-	return union( this.p , a , b ) ;
-} ;
-
-Universe.prototype.find = function ( x ) {
-	return find( this.p , x ) ;
-} ;
+Universe.prototype.union = function (a, b) {
+	return union(this.p, a, b);
+};
 
-export default {
-	Universe ,
-	union ,
-	find ,
-} ;
+Universe.prototype.find = function (x) {
+	return find(this.p, x);
+};
diff --git a/src/adt/ForestAmortizedHalving.js b/src/adt/ForestAmortizedHalving.js
index 82abcf2..e9722d5 100644
--- a/src/adt/ForestAmortizedHalving.js
+++ b/src/adt/ForestAmortizedHalving.js
@@ -1,26 +1,16 @@
-import { rankedtreeunion , _RankedTreeUniverse } from '../fundamentals/index.js' ;
+import {rankedtreeunion, _RankedTreeUniverse} from '../fundamentals/index.js';
 
-export const union = rankedtreeunion ;
+export const union = rankedtreeunion;
 
-export function find ( p , node ) {
-
-	let parent = p[node] ;
-
-	for ( ; p[parent] !== parent ; parent = p[node] ) {
-
-		p[node] = p[parent] ;
-		node = p[node] ;
+export const find = (p, node) => {
+	let parent = p[node];
 
+	for (; p[parent] !== parent; parent = p[node]) {
+		p[node] = p[parent];
+		node = p[node];
 	}
 
-	return parent ;
-
-}
-
-export const Universe = _RankedTreeUniverse( union , find ) ;
+	return parent;
+};
 
-export default {
-	Universe ,
-	union ,
-	find ,
-} ;
+export const Universe = _RankedTreeUniverse(union, find);
diff --git a/src/adt/ForestAmortizedRecursive.js b/src/adt/ForestAmortizedRecursive.js
index 1ef0086..1fc176a 100644
--- a/src/adt/ForestAmortizedRecursive.js
+++ b/src/adt/ForestAmortizedRecursive.js
@@ -1,19 +1,11 @@
-import { rankedtreeunion , _RankedTreeUniverse } from '../fundamentals/index.js' ;
+import {rankedtreeunion, _RankedTreeUniverse} from '../fundamentals/index.js';
 
-export const union = rankedtreeunion ;
+export const union = rankedtreeunion;
 
-export function find ( p , node ) {
+export const find = (p, node) => {
+	if (node !== p[node]) p[node] = find(p, p[node]);
 
-	if ( node !== p[node] ) p[node] = find( p , p[node] ) ;
+	return p[node];
+};
 
-	return p[node] ;
-
-}
-
-export const Universe = _RankedTreeUniverse( union , find ) ;
-
-export default {
-	Universe ,
-	union ,
-	find ,
-} ;
+export const Universe = _RankedTreeUniverse(union, find);
diff --git a/src/adt/ForestAmortizedSplitting.js b/src/adt/ForestAmortizedSplitting.js
index 51f0d63..1970bc9 100644
--- a/src/adt/ForestAmortizedSplitting.js
+++ b/src/adt/ForestAmortizedSplitting.js
@@ -1,26 +1,16 @@
-import { rankedtreeunion , _RankedTreeUniverse } from '../fundamentals/index.js' ;
+import {rankedtreeunion, _RankedTreeUniverse} from '../fundamentals/index.js';
 
-export const union = rankedtreeunion ;
+export const union = rankedtreeunion;
 
-export function find ( p , node ) {
-
-	let parent = p[node] ;
-
-	for ( ; p[parent] !== parent ; parent = p[node] ) {
-
-		p[node] = p[parent] ;
-		node = parent ;
+export const find = (p, node) => {
+	let parent = p[node];
 
+	for (; p[parent] !== parent; parent = p[node]) {
+		p[node] = p[parent];
+		node = parent;
 	}
 
-	return parent ;
-
-}
-
-export const Universe = _RankedTreeUniverse( union , find ) ;
+	return parent;
+};
 
-export default {
-	Universe ,
-	union ,
-	find ,
-} ;
+export const Universe = _RankedTreeUniverse(union, find);
diff --git a/src/adt/ForestAmortizedTwoPasses.js b/src/adt/ForestAmortizedTwoPasses.js
index 18bf314..a984ada 100644
--- a/src/adt/ForestAmortizedTwoPasses.js
+++ b/src/adt/ForestAmortizedTwoPasses.js
@@ -1,29 +1,19 @@
-import { rankedtreeunion , _RankedTreeUniverse } from '../fundamentals/index.js' ;
+import {rankedtreeunion, _RankedTreeUniverse} from '../fundamentals/index.js';
 
-export const union = rankedtreeunion ;
+export const union = rankedtreeunion;
 
-export function find ( p , node ) {
+export const find = (p, node) => {
+	let it = node;
 
-	let it = node ;
-
-	for ( ; it !== p[it] ; it = p[it] ) ;
-
-	while ( p[node] !== it ) {
-
-		const parent = p[node] ;
-		p[node] = it ;
-		node = parent ;
+	for (; it !== p[it]; it = p[it]);
 
+	while (p[node] !== it) {
+		const parent = p[node];
+		p[node] = it;
+		node = parent;
 	}
 
-	return it ;
-
-}
-
-export const Universe = _RankedTreeUniverse( union , find ) ;
+	return it;
+};
 
-export default {
-	Universe ,
-	union ,
-	find ,
-} ;
+export const Universe = _RankedTreeUniverse(union, find);
diff --git a/src/adt/LinkedList.js b/src/adt/LinkedList.js
index a8bf6a6..2a20f88 100644
--- a/src/adt/LinkedList.js
+++ b/src/adt/LinkedList.js
@@ -1,36 +1,26 @@
-import { selfs , nulls } from '../fundamentals/index.js' ;
+import {identity, nulls} from '../fundamentals/index.js';
 
-export function union ( back , next , a , b ) {
+export const union = (back, next, a, b) => {
+	next[back[a]] = b;
+	back[a] = back[b];
+	return a;
+};
 
-	next[back[a]] = b ;
-	back[a] = back[b] ;
-	return a ;
+export const find = (next, node) => {
+	while (next[node] !== -1) node = next[node];
 
-}
-
-export function find ( next , node ) {
-
-	while ( next[node] !== -1 ) node = next[node] ;
-
-	return node ;
+	return node;
+};
 
+export function Universe(n, List = Array) {
+	this.back = identity(n, List);
+	this.next = nulls(n, List);
 }
 
-export function Universe ( n , List = Array ) {
-	this.back = selfs( n , List ) ;
-	this.next = nulls( n , List ) ;
-}
-
-Universe.prototype.union = function ( a , b ) {
-	return union( this.back , this.next , a , b ) ;
-} ;
-
-Universe.prototype.find = function ( node ) {
-	return find( this.next , node ) ;
-} ;
+Universe.prototype.union = function (a, b) {
+	return union(this.back, this.next, a, b);
+};
 
-export default {
-	Universe ,
-	union ,
-	find ,
-} ;
+Universe.prototype.find = function (node) {
+	return find(this.next, node);
+};
diff --git a/src/adt/LinkedListWithHead.js b/src/adt/LinkedListWithHead.js
index 64b5230..af5defc 100644
--- a/src/adt/LinkedListWithHead.js
+++ b/src/adt/LinkedListWithHead.js
@@ -1,33 +1,25 @@
-import { selfs , nulls } from '../fundamentals/index.js' ;
+import {identity, nulls} from '../fundamentals/index.js';
 
-export function union ( back , next , a , b ) {
+export const union = (back, next, a, b) => {
+	next[back[a]] = b;
+	back[a] = back[b];
 
-	next[back[a]] = b ;
-	back[a] = back[b] ;
+	for (let c = next[a]; c !== b; c = next[c]) back[c] = back[b];
 
-	for ( let c = next[a] ; c !== b ; c = next[c] ) back[c] = back[b] ;
+	return a;
+};
 
-	return a ;
+export const find = (back, node) => back[node];
 
+export function Universe(n, List = Array) {
+	this.back = identity(n, List);
+	this.next = nulls(n, List);
 }
 
-export const find = ( back , node ) => back[node] ;
+Universe.prototype.union = function (a, b) {
+	return union(this.back, this.next, a, b);
+};
 
-export function Universe ( n , List = Array) {
-	this.back = selfs( n , List ) ;
-	this.next = nulls( n , List ) ;
-}
-
-Universe.prototype.union = function ( a , b ) {
-	return union( this.back , this.next , a , b ) ;
-} ;
-
-Universe.prototype.find = function ( node ) {
-	return find( this.back , node ) ;
-} ;
-
-export default {
-	Universe ,
-	union ,
-	find ,
-} ;
+Universe.prototype.find = function (node) {
+	return find(this.back, node);
+};
diff --git a/src/adt/LinkedListWithHeadAndLength.js b/src/adt/LinkedListWithHeadAndLength.js
index a0e4ecd..f5e5926 100644
--- a/src/adt/LinkedListWithHeadAndLength.js
+++ b/src/adt/LinkedListWithHeadAndLength.js
@@ -1,42 +1,34 @@
-import { selfs , nulls , ones } from '../fundamentals/index.js' ;
+import {identity, nulls, ones} from '../fundamentals/index.js';
 
-export function union ( back , next , length , a , b ) {
-
-	if ( length[a] < length[b] ) {
-		let c = a ;
-		a = b ;
-		b = c ;
+export const union = (back, next, length, a, b) => {
+	if (length[a] < length[b]) {
+		const c = a;
+		a = b;
+		b = c;
 	}
 
-	next[back[a]] = b ;
-	back[a] = back[b] ;
-
-	for ( let c = next[a] ; c !== b ; c = next[c] ) back[c] = back[b] ;
+	next[back[a]] = b;
+	back[a] = back[b];
 
-	length[a] += length[b] ;
+	for (let c = next[a]; c !== b; c = next[c]) back[c] = back[b];
 
-	return a ;
+	length[a] += length[b];
 
-}
+	return a;
+};
 
-export const find = ( back , node ) => back[node] ;
+export const find = (back, node) => back[node];
 
-export function Universe ( n , List = Array ) {
-	this.back = selfs( n , List ) ;
-	this.next = nulls( n , List ) ;
-	this._length = ones( n , List ) ;
+export function Universe(n, List = Array) {
+	this.back = identity(n, List);
+	this.next = nulls(n, List);
+	this._length = ones(n, List);
 }
 
-Universe.prototype.union = function ( a , b ) {
-	return union( this.back , this.next , this._length , a , b ) ;
-} ;
-
-Universe.prototype.find = function ( node ) {
-	return find( this.back , node ) ;
-} ;
+Universe.prototype.union = function (a, b) {
+	return union(this.back, this.next, this._length, a, b);
+};
 
-export default {
-	Universe ,
-	union ,
-	find ,
-} ;
+Universe.prototype.find = function (node) {
+	return find(this.back, node);
+};
diff --git a/src/adt/index.js b/src/adt/index.js
index 28ae976..43ebe90 100644
--- a/src/adt/index.js
+++ b/src/adt/index.js
@@ -1,30 +1,8 @@
-import Forest from './Forest.js' ;
-import ForestAmortizedHalving from './ForestAmortizedHalving.js' ;
-import ForestAmortizedRecursive from './ForestAmortizedRecursive.js' ;
-import ForestAmortizedSplitting from './ForestAmortizedSplitting.js' ;
-import ForestAmortizedTwoPasses from './ForestAmortizedTwoPasses.js' ;
-import LinkedList from './LinkedList.js' ;
-import LinkedListWithHead from './LinkedListWithHead.js' ;
-import LinkedListWithHeadAndLength from './LinkedListWithHeadAndLength.js' ;
-
-export default {
-	Forest ,
-	ForestAmortizedHalving ,
-	ForestAmortizedRecursive ,
-	ForestAmortizedSplitting ,
-	ForestAmortizedTwoPasses ,
-	LinkedList ,
-	LinkedListWithHead ,
-	LinkedListWithHeadAndLength ,
-} ;
-
-export {
-	Forest ,
-	ForestAmortizedHalving ,
-	ForestAmortizedRecursive ,
-	ForestAmortizedSplitting ,
-	ForestAmortizedTwoPasses ,
-	LinkedList ,
-	LinkedListWithHead ,
-	LinkedListWithHeadAndLength ,
-} ;
+export * as Forest from './Forest.js';
+export * as ForestAmortizedRecursive from './ForestAmortizedRecursive.js';
+export * as ForestAmortizedHalving from './ForestAmortizedHalving.js';
+export * as ForestAmortizedTwoPasses from './ForestAmortizedTwoPasses.js';
+export * as ForestAmortizedSplitting from './ForestAmortizedSplitting.js';
+export * as LinkedList from './LinkedList.js';
+export * as LinkedListWithHeadAndLength from './LinkedListWithHeadAndLength.js';
+export * as LinkedListWithHead from './LinkedListWithHead.js';
diff --git a/src/fundamentals/_RankedTreeUniverse.js b/src/fundamentals/_RankedTreeUniverse.js
index cdc3f37..b0b3d4a 100644
--- a/src/fundamentals/_RankedTreeUniverse.js
+++ b/src/fundamentals/_RankedTreeUniverse.js
@@ -1,21 +1,19 @@
-import selfs from './selfs.js' ;
-import zeros from './zeros.js' ;
+import identity from './identity.js';
+import zeros from './zeros.js';
 
-export default function _RankedTreeUniverse ( union , find ) {
+export default function _RankedTreeUniverse(union, find) {
+	const Universe = function (n, List = Array) {
+		this.p = identity(n, List);
+		this.r = zeros(n, List);
+	};
 
-	const Universe = function ( n , List = Array ) {
-		this.p = selfs( n , List ) ;
-		this.r = zeros( n , List ) ;
-	} ;
+	Universe.prototype.union = function (a, b) {
+		return union(this.p, this.r, a, b);
+	};
 
-	Universe.prototype.union = function ( a , b ) {
-		return union( this.p , this.r , a , b ) ;
-	} ;
-
-	Universe.prototype.find = function ( x ) {
-		return find( this.p , x ) ;
-	} ;
-
-	return Universe ;
+	Universe.prototype.find = function (x) {
+		return find(this.p, x);
+	};
 
+	return Universe;
 }
diff --git a/src/fundamentals/identity.js b/src/fundamentals/identity.js
new file mode 100644
index 0000000..754bc34
--- /dev/null
+++ b/src/fundamentals/identity.js
@@ -0,0 +1,7 @@
+export default function identity(n, List = Array) {
+	const a = new List(n);
+
+	for (let i = 0; i < n; ++i) a[i] = i;
+
+	return a;
+}
diff --git a/src/fundamentals/index.js b/src/fundamentals/index.js
index 69c60bc..1559bf2 100644
--- a/src/fundamentals/index.js
+++ b/src/fundamentals/index.js
@@ -1,24 +1,6 @@
-import _RankedTreeUniverse from './_RankedTreeUniverse.js' ;
-import nulls from './nulls.js' ;
-import ones from './ones.js' ;
-import rankedtreeunion from './rankedtreeunion.js' ;
-import selfs from './selfs.js' ;
-import zeros from './zeros.js' ;
-
-export default {
-	_RankedTreeUniverse ,
-	nulls ,
-	ones ,
-	rankedtreeunion ,
-	selfs ,
-	zeros ,
-} ;
-
-export {
-	_RankedTreeUniverse ,
-	nulls ,
-	ones ,
-	rankedtreeunion ,
-	selfs ,
-	zeros ,
-} ;
+export {default as _RankedTreeUniverse} from './_RankedTreeUniverse.js';
+export {default as ones} from './ones.js';
+export {default as nulls} from './nulls.js';
+export {default as identity} from './identity.js';
+export {default as rankedtreeunion} from './rankedtreeunion.js';
+export {default as zeros} from './zeros.js';
diff --git a/src/fundamentals/nulls.js b/src/fundamentals/nulls.js
index f80ae3e..5ab6eff 100644
--- a/src/fundamentals/nulls.js
+++ b/src/fundamentals/nulls.js
@@ -1,9 +1,7 @@
-export default function nulls ( n , List = Array ) {
+export default function nulls(n, List = Array) {
+	const a = new List(n);
 
-	const a = new List( n ) ;
-
-	for ( let i = 0 ; i < n ; ++i ) a[i] = -1 ;
-
-	return a ;
+	for (let i = 0; i < n; ++i) a[i] = -1;
 
+	return a;
 }
diff --git a/src/fundamentals/ones.js b/src/fundamentals/ones.js
index 7f055e9..1ac4087 100644
--- a/src/fundamentals/ones.js
+++ b/src/fundamentals/ones.js
@@ -1,9 +1,7 @@
-export default function ones ( n , List = Array ) {
+export default function ones(n, List = Array) {
+	const a = new List(n);
 
-	const a = new List( n ) ;
-
-	for ( let i = 0 ; i < n ; ++i ) a[i] = 1 ;
-
-	return a ;
+	for (let i = 0; i < n; ++i) a[i] = 1;
 
+	return a;
 }
diff --git a/src/fundamentals/rankedtreeunion.js b/src/fundamentals/rankedtreeunion.js
index c7f8afa..2296f15 100644
--- a/src/fundamentals/rankedtreeunion.js
+++ b/src/fundamentals/rankedtreeunion.js
@@ -1,19 +1,15 @@
-export default function rankedtreeunion ( p , r , a , b ) {
-
-	if ( r[a] < r[b] ) {
-		p[a] = b ;
-		return b ;
-	}
-
-	else if ( r[a] > r[b] ) {
-		p[b] = a ;
-		return a ;
+export default function rankedtreeunion(p, r, a, b) {
+	if (r[a] < r[b]) {
+		p[a] = b;
+		return b;
 	}
 
-	else {
-		p[b] = a ;
-		++r[a] ;
-		return a ;
+	if (r[a] > r[b]) {
+		p[b] = a;
+		return a;
 	}
 
+	p[b] = a;
+	++r[a];
+	return a;
 }
diff --git a/src/fundamentals/selfs.js b/src/fundamentals/selfs.js
deleted file mode 100644
index 43a2c27..0000000
--- a/src/fundamentals/selfs.js
+++ /dev/null
@@ -1,9 +0,0 @@
-export default function selfs ( n , List = Array ) {
-
-	const a = new List( n ) ;
-
-	for ( let i = 0 ; i < n ; ++i ) a[i] = i ;
-
-	return a ;
-
-}
diff --git a/src/fundamentals/zeros.js b/src/fundamentals/zeros.js
index df16ad4..7ea0053 100644
--- a/src/fundamentals/zeros.js
+++ b/src/fundamentals/zeros.js
@@ -1,9 +1,7 @@
-export default function zeros ( n , List = Array ) {
+export default function zeros(n, List = Array) {
+	const a = new List(n);
 
-	const a = new List( n ) ;
-
-	for ( let i = 0 ; i < n ; ++i ) a[i] = 0 ;
-
-	return a ;
+	for (let i = 0; i < n; ++i) a[i] = 0;
 
+	return a;
 }
diff --git a/src/index.js b/src/index.js
index 49b5cee..d2e94e5 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,32 +1,10 @@
-import {
-	Forest ,
-	ForestAmortizedHalving ,
-	ForestAmortizedRecursive ,
-	ForestAmortizedSplitting ,
-	ForestAmortizedTwoPasses ,
-	LinkedList ,
-	LinkedListWithHead ,
-	LinkedListWithHeadAndLength ,
-} from './adt/index.js' ;
-
-export default {
-	Forest ,
-	ForestAmortizedHalving ,
-	ForestAmortizedRecursive ,
-	ForestAmortizedSplitting ,
-	ForestAmortizedTwoPasses ,
-	LinkedList ,
-	LinkedListWithHead ,
-	LinkedListWithHeadAndLength ,
-} ;
-
 export {
-	Forest ,
-	ForestAmortizedHalving ,
-	ForestAmortizedRecursive ,
-	ForestAmortizedSplitting ,
-	ForestAmortizedTwoPasses ,
-	LinkedList ,
-	LinkedListWithHead ,
-	LinkedListWithHeadAndLength ,
-} ;
+	Forest,
+	ForestAmortizedRecursive,
+	ForestAmortizedHalving,
+	ForestAmortizedTwoPasses,
+	ForestAmortizedSplitting,
+	LinkedList,
+	LinkedListWithHeadAndLength,
+	LinkedListWithHead,
+} from './adt/index.js';
diff --git a/test/src/disjointset.js b/test/src/disjointset.js
index 9a098c5..7833a2c 100644
--- a/test/src/disjointset.js
+++ b/test/src/disjointset.js
@@ -1,131 +1,343 @@
-import test from 'ava' ;
+import test from 'ava';
 
 import {
-	LinkedList ,
-	LinkedListWithHead ,
-	LinkedListWithHeadAndLength ,
-	Forest ,
-	ForestAmortizedRecursive ,
-	ForestAmortizedTwoPasses ,
-	ForestAmortizedSplitting ,
-	ForestAmortizedHalving ,
-} from '../../src/index.js' ;
+	LinkedList,
+	LinkedListWithHead,
+	LinkedListWithHeadAndLength,
+	Forest,
+	ForestAmortizedRecursive,
+	ForestAmortizedTwoPasses,
+	ForestAmortizedSplitting,
+	ForestAmortizedHalving,
+} from '../../src/index.js';
 
-function macro ( t , Universe ) {
+function macro(t, Universe) {
+	/* eslint-disable no-multi-assign */
+	let a;
+	let b;
+	let c;
+	let d;
+	let e;
+	let A;
+	let B;
+	let C;
+	let D;
+	let E;
+	let U;
 
-	let a , b , c , d , e , A , B , C , D , E , U ;
+	// eslint-disable-next-line unicorn/no-array-callback-reference
+	const l = (x, y) => t.true(U.find(x) === U.find(y));
 
-	const l = ( x , y ) => t.true( U.find( x ) === U.find( y ) ) ;
-
-	const o = ( x , y ) => t.true( U.find( x ) !== U.find( y ) ) ;
+	// eslint-disable-next-line unicorn/no-array-callback-reference
+	const o = (x, y) => t.true(U.find(x) !== U.find(y));
 
 	// 1st scenario
-	U = new Universe( 5 ) ;
+	U = new Universe(5);
 
-	A = a = 0 ;
-	B = b = 1 ;
-	C = c = 2 ;
-	D = d = 3 ;
-	E = e = 4 ;
+	A = a = 0;
+	B = b = 1;
+	C = c = 2;
+	D = d = 3;
+	E = e = 4;
 
-	l( a , a ) ; o( b , a ) ; o( c , a ) ; o( d , a ) ; o( e , a ) ;
-	o( a , b ) ; l( b , b ) ; o( c , b ) ; o( d , b ) ; o( e , b ) ;
-	o( a , c ) ; o( b , c ) ; l( c , c ) ; o( d , c ) ; o( e , c ) ;
-	o( a , d ) ; o( b , d ) ; o( c , d ) ; l( d , d ) ; o( e , d ) ;
-	o( a , e ) ; o( b , e ) ; o( c , e ) ; o( d , e ) ; l( e , e ) ;
+	l(a, a);
+	o(b, a);
+	o(c, a);
+	o(d, a);
+	o(e, a);
+	o(a, b);
+	l(b, b);
+	o(c, b);
+	o(d, b);
+	o(e, b);
+	o(a, c);
+	o(b, c);
+	l(c, c);
+	o(d, c);
+	o(e, c);
+	o(a, d);
+	o(b, d);
+	o(c, d);
+	l(d, d);
+	o(e, d);
+	o(a, e);
+	o(b, e);
+	o(c, e);
+	o(d, e);
+	l(e, e);
 
-	A = U.union( A , E ) ;
+	A = U.union(A, E);
 
-	l( a , a ) ; o( b , a ) ; o( c , a ) ; o( d , a ) ; l( e , a ) ;
-	o( a , b ) ; l( b , b ) ; o( c , b ) ; o( d , b ) ; o( e , b ) ;
-	o( a , c ) ; o( b , c ) ; l( c , c ) ; o( d , c ) ; o( e , c ) ;
-	o( a , d ) ; o( b , d ) ; o( c , d ) ; l( d , d ) ; o( e , d ) ;
-	l( a , e ) ; o( b , e ) ; o( c , e ) ; o( d , e ) ; l( e , e ) ;
+	l(a, a);
+	o(b, a);
+	o(c, a);
+	o(d, a);
+	l(e, a);
+	o(a, b);
+	l(b, b);
+	o(c, b);
+	o(d, b);
+	o(e, b);
+	o(a, c);
+	o(b, c);
+	l(c, c);
+	o(d, c);
+	o(e, c);
+	o(a, d);
+	o(b, d);
+	o(c, d);
+	l(d, d);
+	o(e, d);
+	l(a, e);
+	o(b, e);
+	o(c, e);
+	o(d, e);
+	l(e, e);
 
-	B = U.union( D , B ) ;
+	B = U.union(D, B);
 
-	l( a , a ) ; o( b , a ) ; o( c , a ) ; o( d , a ) ; l( e , a ) ;
-	o( a , b ) ; l( b , b ) ; o( c , b ) ; l( d , b ) ; o( e , b ) ;
-	o( a , c ) ; o( b , c ) ; l( c , c ) ; o( d , c ) ; o( e , c ) ;
-	o( a , d ) ; l( b , d ) ; o( c , d ) ; l( d , d ) ; o( e , d ) ;
-	l( a , e ) ; o( b , e ) ; o( c , e ) ; o( d , e ) ; l( e , e ) ;
+	l(a, a);
+	o(b, a);
+	o(c, a);
+	o(d, a);
+	l(e, a);
+	o(a, b);
+	l(b, b);
+	o(c, b);
+	l(d, b);
+	o(e, b);
+	o(a, c);
+	o(b, c);
+	l(c, c);
+	o(d, c);
+	o(e, c);
+	o(a, d);
+	l(b, d);
+	o(c, d);
+	l(d, d);
+	o(e, d);
+	l(a, e);
+	o(b, e);
+	o(c, e);
+	o(d, e);
+	l(e, e);
 
-	A = U.union( C , A ) ;
+	A = U.union(C, A);
 
-	l( a , a ) ; o( b , a ) ; l( c , a ) ; o( d , a ) ; l( e , a ) ;
-	o( a , b ) ; l( b , b ) ; o( c , b ) ; l( d , b ) ; o( e , b ) ;
-	l( a , c ) ; o( b , c ) ; l( c , c ) ; o( d , c ) ; l( e , c ) ;
-	o( a , d ) ; l( b , d ) ; o( c , d ) ; l( d , d ) ; o( e , d ) ;
-	l( a , e ) ; o( b , e ) ; l( c , e ) ; o( d , e ) ; l( e , e ) ;
+	l(a, a);
+	o(b, a);
+	l(c, a);
+	o(d, a);
+	l(e, a);
+	o(a, b);
+	l(b, b);
+	o(c, b);
+	l(d, b);
+	o(e, b);
+	l(a, c);
+	o(b, c);
+	l(c, c);
+	o(d, c);
+	l(e, c);
+	o(a, d);
+	l(b, d);
+	o(c, d);
+	l(d, d);
+	o(e, d);
+	l(a, e);
+	o(b, e);
+	l(c, e);
+	o(d, e);
+	l(e, e);
 
-	A = U.union( B , A ) ;
+	A = U.union(B, A);
 
-	l( a , a ) ; l( b , a ) ; l( c , a ) ; l( d , a ) ; l( e , a ) ;
-	l( a , b ) ; l( b , b ) ; l( c , b ) ; l( d , b ) ; l( e , b ) ;
-	l( a , c ) ; l( b , c ) ; l( c , c ) ; l( d , c ) ; l( e , c ) ;
-	l( a , d ) ; l( b , d ) ; l( c , d ) ; l( d , d ) ; l( e , d ) ;
-	l( a , e ) ; l( b , e ) ; l( c , e ) ; l( d , e ) ; l( e , e ) ;
+	l(a, a);
+	l(b, a);
+	l(c, a);
+	l(d, a);
+	l(e, a);
+	l(a, b);
+	l(b, b);
+	l(c, b);
+	l(d, b);
+	l(e, b);
+	l(a, c);
+	l(b, c);
+	l(c, c);
+	l(d, c);
+	l(e, c);
+	l(a, d);
+	l(b, d);
+	l(c, d);
+	l(d, d);
+	l(e, d);
+	l(a, e);
+	l(b, e);
+	l(c, e);
+	l(d, e);
+	l(e, e);
 
 	// 2nd scenario
-	U = new Universe( 5 ) ;
-
-	A = a = 0 ;
-	B = b = 1 ;
-	C = c = 2 ;
-	D = d = 3 ;
-	E = e = 4 ;
-
-	l( a , a ) ; o( b , a ) ; o( c , a ) ; o( d , a ) ; o( e , a ) ;
-	o( a , b ) ; l( b , b ) ; o( c , b ) ; o( d , b ) ; o( e , b ) ;
-	o( a , c ) ; o( b , c ) ; l( c , c ) ; o( d , c ) ; o( e , c ) ;
-	o( a , d ) ; o( b , d ) ; o( c , d ) ; l( d , d ) ; o( e , d ) ;
-	o( a , e ) ; o( b , e ) ; o( c , e ) ; o( d , e ) ; l( e , e ) ;
-
-	A = U.union( A , E ) ;
-
-	l( a , a ) ; o( b , a ) ; o( c , a ) ; o( d , a ) ; l( e , a ) ;
-	o( a , b ) ; l( b , b ) ; o( c , b ) ; o( d , b ) ; o( e , b ) ;
-	o( a , c ) ; o( b , c ) ; l( c , c ) ; o( d , c ) ; o( e , c ) ;
-	o( a , d ) ; o( b , d ) ; o( c , d ) ; l( d , d ) ; o( e , d ) ;
-	l( a , e ) ; o( b , e ) ; o( c , e ) ; o( d , e ) ; l( e , e ) ;
-
-	B = U.union( D , B ) ;
-
-	l( a , a ) ; o( b , a ) ; o( c , a ) ; o( d , a ) ; l( e , a ) ;
-	o( a , b ) ; l( b , b ) ; o( c , b ) ; l( d , b ) ; o( e , b ) ;
-	o( a , c ) ; o( b , c ) ; l( c , c ) ; o( d , c ) ; o( e , c ) ;
-	o( a , d ) ; l( b , d ) ; o( c , d ) ; l( d , d ) ; o( e , d ) ;
-	l( a , e ) ; o( b , e ) ; o( c , e ) ; o( d , e ) ; l( e , e ) ;
-
-	A = U.union( A , C ) ;
-
-	l( a , a ) ; o( b , a ) ; l( c , a ) ; o( d , a ) ; l( e , a ) ;
-	o( a , b ) ; l( b , b ) ; o( c , b ) ; l( d , b ) ; o( e , b ) ;
-	l( a , c ) ; o( b , c ) ; l( c , c ) ; o( d , c ) ; l( e , c ) ;
-	o( a , d ) ; l( b , d ) ; o( c , d ) ; l( d , d ) ; o( e , d ) ;
-	l( a , e ) ; o( b , e ) ; l( c , e ) ; o( d , e ) ; l( e , e ) ;
-
-	A = U.union( B , A ) ;
-
-	l( a , a ) ; l( b , a ) ; l( c , a ) ; l( d , a ) ; l( e , a ) ;
-	l( a , b ) ; l( b , b ) ; l( c , b ) ; l( d , b ) ; l( e , b ) ;
-	l( a , c ) ; l( b , c ) ; l( c , c ) ; l( d , c ) ; l( e , c ) ;
-	l( a , d ) ; l( b , d ) ; l( c , d ) ; l( d , d ) ; l( e , d ) ;
-	l( a , e ) ; l( b , e ) ; l( c , e ) ; l( d , e ) ; l( e , e ) ;
-
-} ;
-
-for ( const [ name , Set ] of [
-	[ "LinkedList" , LinkedList ] ,
-	[ "LinkedListWithHead" , LinkedListWithHead ] ,
-	[ "LinkedListWithHeadAndLength" , LinkedListWithHeadAndLength ] ,
-	[ "Forest" , Forest ] ,
-	[ "ForestAmortizedRecursive" , ForestAmortizedRecursive ] ,
-	[ "ForestAmortizedTwoPasses" , ForestAmortizedTwoPasses ] ,
-	[ "ForestAmortizedSplitting" , ForestAmortizedSplitting ] ,
-	[ "ForestAmortizedHalving" , ForestAmortizedHalving ] ,
-] ) {
-
-	test( name , macro , Set.Universe ) ;
+	U = new Universe(5);
+
+	A = a = 0;
+	B = b = 1;
+	C = c = 2;
+	D = d = 3;
+	E = e = 4;
+
+	l(a, a);
+	o(b, a);
+	o(c, a);
+	o(d, a);
+	o(e, a);
+	o(a, b);
+	l(b, b);
+	o(c, b);
+	o(d, b);
+	o(e, b);
+	o(a, c);
+	o(b, c);
+	l(c, c);
+	o(d, c);
+	o(e, c);
+	o(a, d);
+	o(b, d);
+	o(c, d);
+	l(d, d);
+	o(e, d);
+	o(a, e);
+	o(b, e);
+	o(c, e);
+	o(d, e);
+	l(e, e);
+
+	A = U.union(A, E);
+
+	l(a, a);
+	o(b, a);
+	o(c, a);
+	o(d, a);
+	l(e, a);
+	o(a, b);
+	l(b, b);
+	o(c, b);
+	o(d, b);
+	o(e, b);
+	o(a, c);
+	o(b, c);
+	l(c, c);
+	o(d, c);
+	o(e, c);
+	o(a, d);
+	o(b, d);
+	o(c, d);
+	l(d, d);
+	o(e, d);
+	l(a, e);
+	o(b, e);
+	o(c, e);
+	o(d, e);
+	l(e, e);
+
+	B = U.union(D, B);
+
+	l(a, a);
+	o(b, a);
+	o(c, a);
+	o(d, a);
+	l(e, a);
+	o(a, b);
+	l(b, b);
+	o(c, b);
+	l(d, b);
+	o(e, b);
+	o(a, c);
+	o(b, c);
+	l(c, c);
+	o(d, c);
+	o(e, c);
+	o(a, d);
+	l(b, d);
+	o(c, d);
+	l(d, d);
+	o(e, d);
+	l(a, e);
+	o(b, e);
+	o(c, e);
+	o(d, e);
+	l(e, e);
+
+	A = U.union(A, C);
+
+	l(a, a);
+	o(b, a);
+	l(c, a);
+	o(d, a);
+	l(e, a);
+	o(a, b);
+	l(b, b);
+	o(c, b);
+	l(d, b);
+	o(e, b);
+	l(a, c);
+	o(b, c);
+	l(c, c);
+	o(d, c);
+	l(e, c);
+	o(a, d);
+	l(b, d);
+	o(c, d);
+	l(d, d);
+	o(e, d);
+	l(a, e);
+	o(b, e);
+	l(c, e);
+	o(d, e);
+	l(e, e);
+
+	// eslint-disable-next-line no-unused-vars
+	A = U.union(B, A);
+
+	l(a, a);
+	l(b, a);
+	l(c, a);
+	l(d, a);
+	l(e, a);
+	l(a, b);
+	l(b, b);
+	l(c, b);
+	l(d, b);
+	l(e, b);
+	l(a, c);
+	l(b, c);
+	l(c, c);
+	l(d, c);
+	l(e, c);
+	l(a, d);
+	l(b, d);
+	l(c, d);
+	l(d, d);
+	l(e, d);
+	l(a, e);
+	l(b, e);
+	l(c, e);
+	l(d, e);
+	l(e, e);
+
+	/* eslint-enable no-multi-assign */
+}
 
+for (const [name, DisjointSet] of [
+	['LinkedList', LinkedList],
+	['LinkedListWithHead', LinkedListWithHead],
+	['LinkedListWithHeadAndLength', LinkedListWithHeadAndLength],
+	['Forest', Forest],
+	['ForestAmortizedRecursive', ForestAmortizedRecursive],
+	['ForestAmortizedTwoPasses', ForestAmortizedTwoPasses],
+	['ForestAmortizedSplitting', ForestAmortizedSplitting],
+	['ForestAmortizedHalving', ForestAmortizedHalving],
+]) {
+	test(name, macro, DisjointSet.Universe);
 }