diff --git a/test/parallel/test-c-ares.js b/test/parallel/test-c-ares.js
index 0da5d5210c..2eb824b5df 100644
--- a/test/parallel/test-c-ares.js
+++ b/test/parallel/test-c-ares.js
@@ -7,30 +7,29 @@ const dns = require('dns');
 
 // Try resolution without callback
 
-dns.lookup(null, common.mustCall(function(error, result, addressType) {
+dns.lookup(null, common.mustCall((error, result, addressType) => {
+  assert.ifError(error);
   assert.strictEqual(null, result);
   assert.strictEqual(4, addressType);
 }));
 
-dns.lookup('127.0.0.1', common.mustCall(function(error, result, addressType) {
+dns.lookup('127.0.0.1', common.mustCall((error, result, addressType) => {
+  assert.ifError(error);
   assert.strictEqual('127.0.0.1', result);
   assert.strictEqual(4, addressType);
 }));
 
-dns.lookup('::1', common.mustCall(function(error, result, addressType) {
+dns.lookup('::1', common.mustCall((error, result, addressType) => {
+  assert.ifError(error);
   assert.strictEqual('::1', result);
   assert.strictEqual(6, addressType);
 }));
 
 // Try calling resolve with an unsupported type.
-assert.throws(function() {
-  dns.resolve('www.google.com', 'HI');
-}, /Unknown type/);
+assert.throws(() => dns.resolve('www.google.com', 'HI'), /Unknown type/);
 
 // Try calling resolve with an unsupported type that's an object key
-assert.throws(function() {
-  dns.resolve('www.google.com', 'toString');
-}, /Unknown type/);
+assert.throws(() => dns.resolve('www.google.com', 'toString'), /Unknown type/);
 
 // Windows doesn't usually have an entry for localhost 127.0.0.1 in
 // C:\Windows\System32\drivers\etc\hosts
diff --git a/test/parallel/test-dns-lookup-cb-error.js b/test/parallel/test-dns-lookup-cb-error.js
index 4a3dd26941..212f037868 100644
--- a/test/parallel/test-dns-lookup-cb-error.js
+++ b/test/parallel/test-dns-lookup-cb-error.js
@@ -1,22 +1,23 @@
 'use strict';
-require('../common');
-var assert = require('assert');
-var cares = process.binding('cares_wrap');
+const common = require('../common');
+const assert = require('assert');
+const cares = process.binding('cares_wrap');
 
-var dns = require('dns');
+const dns = require('dns');
 
 // Stub `getaddrinfo` to *always* error.
 cares.getaddrinfo = function() {
   return process.binding('uv').UV_ENOENT;
 };
 
-assert.doesNotThrow(function() {
+assert.doesNotThrow(() => {
   var tickValue = 0;
 
-  dns.lookup('example.com', function(error, result, addressType) {
-    assert.equal(tickValue, 1);
-    assert.equal(error.code, 'ENOENT');
-  });
+  dns.lookup('example.com', common.mustCall((error, result, addressType) => {
+    assert(error);
+    assert.strictEqual(tickValue, 1);
+    assert.strictEqual(error.code, 'ENOENT');
+  }));
 
   // Make sure that the error callback is called
   // on next tick.
diff --git a/test/parallel/test-dns-regress-6244.js b/test/parallel/test-dns-regress-6244.js
index 7ed7a89206..b464c7bda8 100644
--- a/test/parallel/test-dns-regress-6244.js
+++ b/test/parallel/test-dns-regress-6244.js
@@ -1,6 +1,6 @@
 'use strict';
-var common = require('../common');
-var dns = require('dns');
+const common = require('../common');
+const dns = require('dns');
 
 // Should not segfault, see #6244.
-dns.resolve4('127.0.0.1', common.mustCall(function() { }));
+dns.resolve4('127.0.0.1', common.mustCall(() => { }));
diff --git a/test/parallel/test-dns-regress-7070.js b/test/parallel/test-dns-regress-7070.js
index e696327d4d..25cf60cf6a 100644
--- a/test/parallel/test-dns-regress-7070.js
+++ b/test/parallel/test-dns-regress-7070.js
@@ -1,8 +1,8 @@
 'use strict';
 require('../common');
-var assert = require('assert');
-var dns = require('dns');
+const assert = require('assert');
+const dns = require('dns');
 
 // Should not raise assertion error. Issue #7070
-assert.throws(function() { dns.resolveNs([]); }); // bad name
-assert.throws(function() { dns.resolveNs(''); }); // bad callback
+assert.throws(() => dns.resolveNs([])); // bad name
+assert.throws(() => dns.resolveNs('')); // bad callback
diff --git a/test/parallel/test-dns.js b/test/parallel/test-dns.js
index cf3b76c71e..5fcc045b2e 100644
--- a/test/parallel/test-dns.js
+++ b/test/parallel/test-dns.js
@@ -4,7 +4,7 @@ const assert = require('assert');
 
 const dns = require('dns');
 
-var existing = dns.getServers();
+const existing = dns.getServers();
 assert(existing.length);
 
 // Verify that setServers() handles arrays with holes and other oddities
@@ -36,86 +36,71 @@ assert.doesNotThrow(() => {
 
 function noop() {}
 
-var goog = [
+const goog = [
   '8.8.8.8',
   '8.8.4.4',
 ];
-assert.doesNotThrow(function() { dns.setServers(goog); });
+assert.doesNotThrow(() => dns.setServers(goog));
 assert.deepStrictEqual(dns.getServers(), goog);
-assert.throws(function() { dns.setServers(['foobar']); });
+assert.throws(() => dns.setServers(['foobar']));
 assert.deepStrictEqual(dns.getServers(), goog);
 
-var goog6 = [
+const goog6 = [
   '2001:4860:4860::8888',
   '2001:4860:4860::8844',
 ];
-assert.doesNotThrow(function() { dns.setServers(goog6); });
+assert.doesNotThrow(() => dns.setServers(goog6));
 assert.deepStrictEqual(dns.getServers(), goog6);
 
 goog6.push('4.4.4.4');
 dns.setServers(goog6);
 assert.deepStrictEqual(dns.getServers(), goog6);
 
-var ports = [
+const ports = [
   '4.4.4.4:53',
   '[2001:4860:4860::8888]:53',
 ];
-var portsExpected = [
+const portsExpected = [
   '4.4.4.4',
   '2001:4860:4860::8888',
 ];
 dns.setServers(ports);
 assert.deepStrictEqual(dns.getServers(), portsExpected);
 
-assert.doesNotThrow(function() { dns.setServers([]); });
+assert.doesNotThrow(() => dns.setServers([]));
 assert.deepStrictEqual(dns.getServers(), []);
 
-assert.throws(function() {
+assert.throws(() => {
   dns.resolve('test.com', [], noop);
 }, function(err) {
   return !(err instanceof TypeError);
 }, 'Unexpected error');
 
 // dns.lookup should accept falsey and string values
-assert.throws(function() {
-  dns.lookup({}, noop);
-}, 'invalid arguments: hostname must be a string or falsey');
+assert.throws(() => dns.lookup({}, noop),
+              'invalid arguments: hostname must be a string or falsey');
 
-assert.throws(function() {
-  dns.lookup([], noop);
-}, 'invalid arguments: hostname must be a string or falsey');
+assert.throws(() => dns.lookup([], noop),
+              'invalid arguments: hostname must be a string or falsey');
 
-assert.throws(function() {
-  dns.lookup(true, noop);
-}, 'invalid arguments: hostname must be a string or falsey');
+assert.throws(() => dns.lookup(true, noop),
+              'invalid arguments: hostname must be a string or falsey');
 
-assert.throws(function() {
-  dns.lookup(1, noop);
-}, 'invalid arguments: hostname must be a string or falsey');
+assert.throws(() => dns.lookup(1, noop),
+              'invalid arguments: hostname must be a string or falsey');
 
-assert.throws(function() {
-  dns.lookup(noop, noop);
-}, 'invalid arguments: hostname must be a string or falsey');
+assert.throws(() => dns.lookup(noop, noop),
+              'invalid arguments: hostname must be a string or falsey');
 
-assert.doesNotThrow(function() {
-  dns.lookup('', noop);
-});
+assert.doesNotThrow(() => dns.lookup('', noop));
 
-assert.doesNotThrow(function() {
-  dns.lookup(null, noop);
-});
+assert.doesNotThrow(() => dns.lookup(null, noop));
 
-assert.doesNotThrow(function() {
-  dns.lookup(undefined, noop);
-});
+assert.doesNotThrow(() => dns.lookup(undefined, noop));
 
-assert.doesNotThrow(function() {
-  dns.lookup(0, noop);
-});
+assert.doesNotThrow(() => dns.lookup(0, noop));
 
-assert.doesNotThrow(function() {
-  dns.lookup(NaN, noop);
-});
+assert.doesNotThrow(() => dns.lookup(NaN, noop));
 
 /*
  * Make sure that dns.lookup throws if hints does not represent a valid flag.
@@ -126,85 +111,58 @@ assert.doesNotThrow(function() {
  * - it's an odd number different than 1, and thus is invalid, because
  * flags are either === 1 or even.
  */
-assert.throws(function() {
+assert.throws(() => {
   dns.lookup('www.google.com', { hints: (dns.V4MAPPED | dns.ADDRCONFIG) + 1 },
     noop);
 });
 
-assert.throws(function() {
-  dns.lookup('www.google.com');
-}, 'invalid arguments: callback must be passed');
+assert.throws(() => dns.lookup('www.google.com'),
+              'invalid arguments: callback must be passed');
 
-assert.throws(function() {
-  dns.lookup('www.google.com', 4);
-}, 'invalid arguments: callback must be passed');
+assert.throws(() => dns.lookup('www.google.com', 4),
+              'invalid arguments: callback must be passed');
 
-assert.doesNotThrow(function() {
-  dns.lookup('www.google.com', 6, noop);
-});
+assert.doesNotThrow(() => dns.lookup('www.google.com', 6, noop));
 
-assert.doesNotThrow(function() {
-  dns.lookup('www.google.com', {}, noop);
-});
+assert.doesNotThrow(() => dns.lookup('www.google.com', {}, noop));
 
-assert.doesNotThrow(function() {
-  dns.lookup('', {
-    family: 4,
-    hints: 0
-  }, noop);
-});
+assert.doesNotThrow(() => dns.lookup('', {family: 4, hints: 0}, noop));
 
-assert.doesNotThrow(function() {
+assert.doesNotThrow(() => {
   dns.lookup('', {
     family: 6,
     hints: dns.ADDRCONFIG
   }, noop);
 });
 
-assert.doesNotThrow(function() {
-  dns.lookup('', {
-    hints: dns.V4MAPPED
-  }, noop);
-});
+assert.doesNotThrow(() => dns.lookup('', {hints: dns.V4MAPPED}, noop));
 
-assert.doesNotThrow(function() {
+assert.doesNotThrow(() => {
   dns.lookup('', {
     hints: dns.ADDRCONFIG | dns.V4MAPPED
   }, noop);
 });
 
-assert.throws(function() {
-  dns.lookupService('0.0.0.0');
-}, /Invalid arguments/);
+assert.throws(() => dns.lookupService('0.0.0.0'), /Invalid arguments/);
 
-assert.throws(function() {
-  dns.lookupService('fasdfdsaf', 0, noop);
-}, /"host" argument needs to be a valid IP address/);
+assert.throws(() => dns.lookupService('fasdfdsaf', 0, noop),
+              /"host" argument needs to be a valid IP address/);
 
-assert.doesNotThrow(function() {
-  dns.lookupService('0.0.0.0', '0', noop);
-});
+assert.doesNotThrow(() => dns.lookupService('0.0.0.0', '0', noop));
 
-assert.doesNotThrow(function() {
-  dns.lookupService('0.0.0.0', 0, noop);
-});
+assert.doesNotThrow(() => dns.lookupService('0.0.0.0', 0, noop));
 
-assert.throws(function() {
-  dns.lookupService('0.0.0.0', null, noop);
-}, /"port" should be >= 0 and < 65536, got "null"/);
+assert.throws(() => dns.lookupService('0.0.0.0', null, noop),
+              /"port" should be >= 0 and < 65536, got "null"/);
 
-assert.throws(function() {
-  dns.lookupService('0.0.0.0', undefined, noop);
-}, /"port" should be >= 0 and < 65536, got "undefined"/);
+assert.throws(() => dns.lookupService('0.0.0.0', undefined, noop),
+              /"port" should be >= 0 and < 65536, got "undefined"/);
 
-assert.throws(function() {
-  dns.lookupService('0.0.0.0', 65538, noop);
-}, /"port" should be >= 0 and < 65536, got "65538"/);
+assert.throws(() => dns.lookupService('0.0.0.0', 65538, noop),
+              /"port" should be >= 0 and < 65536, got "65538"/);
 
-assert.throws(function() {
-  dns.lookupService('0.0.0.0', 'test', noop);
-}, /"port" should be >= 0 and < 65536, got "test"/);
+assert.throws(() => dns.lookupService('0.0.0.0', 'test', noop),
+              /"port" should be >= 0 and < 65536, got "test"/);
 
-assert.throws(() => {
-  dns.lookupService('0.0.0.0', 80, null);
-}, /^TypeError: "callback" argument must be a function$/);
+assert.throws(() => dns.lookupService('0.0.0.0', 80, null),
+              /^TypeError: "callback" argument must be a function$/);
diff --git a/test/parallel/test-eval-require.js b/test/parallel/test-eval-require.js
index 208013b6d5..35f47a922a 100644
--- a/test/parallel/test-eval-require.js
+++ b/test/parallel/test-eval-require.js
@@ -1,12 +1,12 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
-var spawn = require('child_process').spawn;
+const common = require('../common');
+const assert = require('assert');
+const spawn = require('child_process').spawn;
 
-var options = {
+const options = {
   cwd: common.fixturesDir
 };
-var child = spawn(process.execPath, ['-e', 'require("foo")'], options);
-child.on('exit', function(code) {
-  assert.equal(code, 0);
-});
+const child = spawn(process.execPath, ['-e', 'require("foo")'], options);
+child.on('exit', common.mustCall((code) => {
+  assert.strictEqual(code, 0);
+}));
diff --git a/test/parallel/test-eval.js b/test/parallel/test-eval.js
index b27aa33d84..cddbe86795 100644
--- a/test/parallel/test-eval.js
+++ b/test/parallel/test-eval.js
@@ -4,10 +4,12 @@ const util = require('util');
 const assert = require('assert');
 const exec = require('child_process').exec;
 
-const cmd = ['"' + process.execPath + '"', '-e',
-             '"console.error(process.argv)"', 'foo', 'bar'].join(' ');
+const cmd = [
+  `"${process.execPath}"`, '-e',
+  '"console.error(process.argv)"',
+  'foo', 'bar'].join(' ');
 const expected = util.format([process.execPath, 'foo', 'bar']) + '\n';
-exec(cmd, common.mustCall(function(err, stdout, stderr) {
+exec(cmd, common.mustCall((err, stdout, stderr) => {
   assert.ifError(err);
   assert.strictEqual(stderr, expected);
 }));
diff --git a/test/parallel/test-global.js b/test/parallel/test-global.js
index e43109c903..1bf1bd7cd6 100644
--- a/test/parallel/test-global.js
+++ b/test/parallel/test-global.js
@@ -1,22 +1,23 @@
 /* eslint-disable strict */
-var common = require('../common');
-var path = require('path');
-var assert = require('assert');
+const common = require('../common');
+const path = require('path');
+const assert = require('assert');
 
 common.globalCheck = false;
 
 baseFoo = 'foo'; // eslint-disable-line no-undef
 global.baseBar = 'bar';
 
-assert.equal('foo', global.baseFoo, 'x -> global.x in base level not working');
+assert.strictEqual('foo', global.baseFoo,
+                   'x -> global.x in base level not working');
 
-assert.equal('bar',
-             baseBar, // eslint-disable-line no-undef
-             'global.x -> x in base level not working');
+assert.strictEqual('bar',
+                   baseBar, // eslint-disable-line no-undef
+                   'global.x -> x in base level not working');
 
 var module = require(path.join(common.fixturesDir, 'global', 'plain'));
 const fooBar = module.fooBar;
 
-assert.equal('foo', fooBar.foo, 'x -> global.x in sub level not working');
+assert.strictEqual('foo', fooBar.foo, 'x -> global.x in sub level not working');
 
-assert.equal('bar', fooBar.bar, 'global.x -> x in sub level not working');
+assert.strictEqual('bar', fooBar.bar, 'global.x -> x in sub level not working');