diff --git a/test/headers.js b/test/headers.js
index ef6973d..48a731e 100644
--- a/test/headers.js
+++ b/test/headers.js
@@ -1,5 +1,8 @@
 import {Headers} from '../src/index.js';
 import chai from 'chai';
+import chaiIterator from 'chai-iterator';
+
+chai.use(chaiIterator);
 
 const {expect} = chai;
 
diff --git a/test/main.js b/test/main.js
index 42dcee3..280dc45 100644
--- a/test/main.js
+++ b/test/main.js
@@ -48,17 +48,6 @@ chai.use(chaiString);
 chai.use(chaiTimeout);
 const {expect} = chai;
 
-const local = new TestServer();
-const base = `http://${local.hostname}:${local.port}/`;
-
-before(done => {
-	local.start(done);
-});
-
-after(done => {
-	local.stop(done);
-});
-
 function streamToPromise(stream, dataHandler) {
 	return new Promise((resolve, reject) => {
 		stream.on('data', (...args) => {
@@ -72,6 +61,18 @@ function streamToPromise(stream, dataHandler) {
 }
 
 describe('node-fetch', () => {
+	const local = new TestServer();
+	let base;
+
+	before(async () => {
+		await local.start();
+		base = `http://${local.hostname}:${local.port}/`;
+	});
+
+	after(async () => {
+		return local.stop();
+	});
+
 	it('should return a promise', () => {
 		const url = `${base}hello`;
 		const p = fetch(url);
@@ -2124,9 +2125,9 @@ describe('node-fetch', () => {
 		expect(extractContentType(null)).to.be.null;
 	});
 
-	it('should encode URLs as UTF-8', () => {
+	it('should encode URLs as UTF-8', async () => {
 		const url = `${base}möbius`;
-
-		fetch(url).then(res => expect(res.url).to.equal(`${base}m%C3%B6bius`));
+		const res = await fetch(url);
+		expect(res.url).to.equal(`${base}m%C3%B6bius`);
 	});
 });
diff --git a/test/request.js b/test/request.js
index 9c62245..19fb8af 100644
--- a/test/request.js
+++ b/test/request.js
@@ -13,10 +13,19 @@ import {Request} from '../src/index.js';
 
 const {expect} = chai;
 
-const local = new TestServer();
-const base = `http://${local.hostname}:${local.port}/`;
-
 describe('Request', () => {
+	const local = new TestServer();
+	let base;
+
+	before(async () => {
+		await local.start();
+		base = `http://${local.hostname}:${local.port}/`;
+	});
+
+	after(async () => {
+		return local.stop();
+	});
+
 	it('should have attributes conforming to Web IDL', () => {
 		const request = new Request('https://github.com/');
 		const enumerableProperties = [];
diff --git a/test/response.js b/test/response.js
index da8787d..f02b67f 100644
--- a/test/response.js
+++ b/test/response.js
@@ -8,10 +8,19 @@ import TestServer from './utils/server.js';
 
 const {expect} = chai;
 
-const local = new TestServer();
-const base = `http://${local.hostname}:${local.port}/`;
-
 describe('Response', () => {
+	const local = new TestServer();
+	let base;
+
+	before(async () => {
+		await local.start();
+		base = `http://${local.hostname}:${local.port}/`;
+	});
+
+	after(async () => {
+		return local.stop();
+	});
+
 	it('should have attributes conforming to Web IDL', () => {
 		const res = new Response();
 		const enumerableProperties = [];
diff --git a/test/utils/server.js b/test/utils/server.js
index cc9a9ab..f4c2a5f 100644
--- a/test/utils/server.js
+++ b/test/utils/server.js
@@ -1,12 +1,11 @@
 import http from 'http';
 import zlib from 'zlib';
 import Busboy from 'busboy';
+import {once} from 'events';
 
 export default class TestServer {
 	constructor() {
 		this.server = http.createServer(this.router);
-		this.port = 30001;
-		this.hostname = 'localhost';
 		// Node 8 default keepalive timeout is 5000ms
 		// make it shorter here as we want to close server quickly at the end of tests
 		this.server.keepAliveTimeout = 1000;
@@ -18,12 +17,22 @@ export default class TestServer {
 		});
 	}
 
-	start(cb) {
-		this.server.listen(this.port, this.hostname, cb);
+	async start() {
+		this.server.listen(0, 'localhost');
+		return once(this.server, 'listening');
 	}
 
-	stop(cb) {
-		this.server.close(cb);
+	async stop() {
+		this.server.close();
+		return once(this.server, 'close');
+	}
+
+	get port() {
+		return this.server.address().port;
+	}
+
+	get hostname() {
+		return 'localhost';
 	}
 
 	mockResponse(responseHandler) {