diff --git a/package-lock.json b/package-lock.json
index 9917f97..61db7f1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -214,21 +214,21 @@
       }
     },
     "@google-cloud/common": {
-      "version": "0.19.2",
-      "resolved": "https://registry.npmjs.org/@google-cloud/common/-/common-0.19.2.tgz",
-      "integrity": "sha512-CuURBaMx6vUwLFpHLCYyLJXkg6EKYcrAfhH9Fva8C2B9dJ7flT8j/R+o05OuXwj4VQYC4c8bl/hrwyO+XvAwlg==",
+      "version": "0.20.1",
+      "resolved": "https://registry.npmjs.org/@google-cloud/common/-/common-0.20.1.tgz",
+      "integrity": "sha512-LJB7CoNXEXY0mDWtF8E2cl3Y0kuMQ3wjH9Xr+Y7vH5gHgN82dDh1BMUOizRf9oXQFDWUgGERD5SdfBcjUhHmwA==",
       "requires": {
         "@types/duplexify": "^3.5.0",
         "@types/request": "^2.47.0",
         "arrify": "^1.0.1",
         "axios": "^0.18.0",
-        "duplexify": "^3.5.4",
+        "duplexify": "^3.6.0",
         "ent": "^2.2.0",
         "extend": "^3.0.1",
-        "google-auth-library": "^1.4.0",
+        "google-auth-library": "^1.6.0",
         "is": "^3.2.1",
         "pify": "^3.0.0",
-        "request": "^2.85.0",
+        "request": "^2.87.0",
         "retry-request": "^3.3.1",
         "split-array-stream": "^2.0.0",
         "stream-events": "^1.0.4",
@@ -1947,14 +1947,14 @@
       }
     },
     "@types/node": {
-      "version": "10.3.2",
-      "resolved": "https://registry.npmjs.org/@types/node/-/node-10.3.2.tgz",
-      "integrity": "sha512-9NfEUDp3tgRhmoxzTpTo+lq+KIVFxZahuRX0LHF/9IzKHaWuoWsIrrJ61zw5cnnlGINX8lqJzXYfQTOICS5Q+A=="
+      "version": "10.3.4",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-10.3.4.tgz",
+      "integrity": "sha512-YMLlzdeNnAyLrQew39IFRkMacAR5BqKGIEei9ZjdHsIZtv+ZWKYTu1i7QJhetxQ9ReXx8w5f+cixdHZG3zgMQA=="
     },
     "@types/request": {
-      "version": "2.47.0",
-      "resolved": "https://registry.npmjs.org/@types/request/-/request-2.47.0.tgz",
-      "integrity": "sha512-/KXM5oev+nNCLIgBjkwbk8VqxmzI56woD4VUxn95O+YeQ8hJzcSmIZ1IN3WexiqBb6srzDo2bdMbsXxgXNkz5Q==",
+      "version": "2.47.1",
+      "resolved": "https://registry.npmjs.org/@types/request/-/request-2.47.1.tgz",
+      "integrity": "sha512-TV3XLvDjQbIeVxJ1Z3oCTDk/KuYwwcNKVwz2YaT0F5u86Prgc4syDAp6P96rkTQQ4bIdh+VswQIC9zS6NjY7/g==",
       "requires": {
         "@types/caseless": "*",
         "@types/form-data": "*",
diff --git a/src/change.js b/src/change.js
index a138778..ef5151b 100644
--- a/src/change.js
+++ b/src/change.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+const common = require('@google-cloud/common');
+const util = require('util');
 
 /**
  * @class
@@ -32,7 +32,7 @@ var util = require('util');
  * const change = zone.change('change-id');
  */
 function Change(zone, id) {
-  var methods = {
+  const methods = {
     /**
      * @typedef {array} ChangeExistsResponse
      * @property {boolean} 0 Whether the {@link Change} exists.
@@ -61,7 +61,7 @@ function Change(zone, id) {
      * // If the callback is omitted, we'll return a Promise.
      * //-
      * change.exists().then(function(data) {
-     *   var exists = data[0];
+     *   const exists = data[0];
      * });
      */
     exists: true,
@@ -106,8 +106,8 @@ function Change(zone, id) {
      * // If the callback is omitted, we'll return a Promise.
      * //-
      * change.get().then(function(data) {
-     *   var change = data[0];
-     *   var apiResponse = data[1];
+     *   const change = data[0];
+     *   const apiResponse = data[1];
      * });
      */
     get: true,
@@ -156,8 +156,8 @@ function Change(zone, id) {
      * // If the callback is omitted, we'll return a Promise.
      * //-
      * change.getMetadata().then(function(data) {
-     *   var metadata = data[0];
-     *   var apiResponse = data[1];
+     *   const metadata = data[0];
+     *   const apiResponse = data[1];
      * });
      */
     getMetadata: true,
@@ -223,7 +223,7 @@ util.inherits(Change, common.ServiceObject);
  * });
  */
 Change.prototype.create = function(config, callback) {
-  var self = this;
+  const self = this;
 
   this.parent.createChange(config, function(err, change, apiResponse) {
     if (err) {
diff --git a/src/index.js b/src/index.js
index df2ae6f..2f41567 100644
--- a/src/index.js
+++ b/src/index.js
@@ -16,13 +16,13 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var is = require('is');
-var util = require('util');
+const arrify = require('arrify');
+const common = require('@google-cloud/common');
+const extend = require('extend');
+const is = require('is');
+const util = require('util');
 
-var Zone = require('./zone.js');
+const Zone = require('./zone.js');
 
 /**
  * @typedef {object} ClientConfig
@@ -85,7 +85,7 @@ function DNS(options) {
 
   options = common.util.normalizeArguments(this, options);
 
-  var config = {
+  const config = {
     baseUrl: 'https://www.googleapis.com/dns/v1',
     scopes: [
       'https://www.googleapis.com/auth/ndev.clouddns.readwrite',
@@ -156,7 +156,7 @@ util.inherits(DNS, common.Service);
  * });
  */
 DNS.prototype.createZone = function(name, config, callback) {
-  var self = this;
+  const self = this;
 
   if (!name) {
     throw new Error('A zone name is required.');
@@ -183,7 +183,7 @@ DNS.prototype.createZone = function(name, config, callback) {
         return;
       }
 
-      var zone = self.zone(resp.name);
+      const zone = self.zone(resp.name);
       zone.metadata = resp;
 
       callback(null, zone, resp);
@@ -237,7 +237,7 @@ DNS.prototype.createZone = function(name, config, callback) {
  * });
  */
 DNS.prototype.getZones = function(query, callback) {
-  var self = this;
+  const self = this;
 
   if (is.fn(query)) {
     callback = query;
@@ -255,13 +255,13 @@ DNS.prototype.getZones = function(query, callback) {
         return;
       }
 
-      var zones = arrify(resp.managedZones).map(function(zone) {
-        var zoneInstance = self.zone(zone.name);
+      const zones = arrify(resp.managedZones).map(function(zone) {
+        const zoneInstance = self.zone(zone.name);
         zoneInstance.metadata = zone;
         return zoneInstance;
       });
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, query, {
diff --git a/src/record.js b/src/record.js
index b2d7300..b15d689 100644
--- a/src/record.js
+++ b/src/record.js
@@ -16,10 +16,10 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var format = require('string-format-obj');
+const arrify = require('arrify');
+const common = require('@google-cloud/common');
+const extend = require('extend');
+const format = require('string-format-obj');
 
 /**
  * Create a Resource Record object.
@@ -89,7 +89,7 @@ function Record(zone, type, metadata) {
  * @returns {Record}
  */
 Record.fromZoneRecord_ = function(zone, type, bindData) {
-  var typeToZoneFormat = {
+  const typeToZoneFormat = {
     a: '{ip}',
     aaaa: '{ip}',
     cname: '{alias}',
@@ -101,7 +101,7 @@ Record.fromZoneRecord_ = function(zone, type, bindData) {
     txt: '{txt}',
   };
 
-  var metadata = {
+  const metadata = {
     data: format(typeToZoneFormat[type.toLowerCase()], bindData),
     name: bindData.name,
     ttl: bindData.ttl,
@@ -154,8 +154,8 @@ Record.fromZoneRecord_ = function(zone, type, bindData) {
  * // If the callback is omitted, we'll return a Promise.
  * //-
  * record.delete().then(function(data) {
- *   var change = data[0];
- *   var apiResponse = data[1];
+ *   const change = data[0];
+ *   const apiResponse = data[1];
  * });
  */
 Record.prototype.delete = function(callback) {
@@ -168,7 +168,7 @@ Record.prototype.delete = function(callback) {
  * @returns {object}
  */
 Record.prototype.toJSON = function() {
-  var recordObject = extend({}, this.metadata, {
+  const recordObject = extend({}, this.metadata, {
     type: this.type.toUpperCase(),
   });
 
@@ -186,7 +186,7 @@ Record.prototype.toJSON = function() {
  * @returns {string}
  */
 Record.prototype.toString = function() {
-  var json = this.toJSON();
+  const json = this.toJSON();
 
   return (json.rrdatas || [{}])
     .map(function(data) {
diff --git a/src/zone.js b/src/zone.js
index 5352582..1f588f1 100644
--- a/src/zone.js
+++ b/src/zone.js
@@ -16,20 +16,20 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var common = require('@google-cloud/common');
-var exec = require('methmeth');
-var extend = require('extend');
-var flatten = require('lodash.flatten');
-var fs = require('fs');
-var groupBy = require('lodash.groupby');
-var is = require('is');
-var prop = require('propprop');
-var util = require('util');
-var zonefile = require('dns-zonefile');
-
-var Change = require('./change.js');
-var Record = require('./record.js');
+const arrify = require('arrify');
+const common = require('@google-cloud/common');
+const exec = require('methmeth');
+const extend = require('extend');
+const flatten = require('lodash.flatten');
+const fs = require('fs');
+const groupBy = require('lodash.groupby');
+const is = require('is');
+const prop = require('propprop');
+const util = require('util');
+const zonefile = require('dns-zonefile');
+
+const Change = require('./change.js');
+const Record = require('./record.js');
 
 /**
  * A Zone object is used to interact with your project's managed zone. It will
@@ -45,7 +45,7 @@ var Record = require('./record.js');
  * const zone = dns.zone('zone-id');
  */
 function Zone(dns, name) {
-  var methods = {
+  const methods = {
     /**
      * Create a zone.
      *
@@ -339,13 +339,13 @@ Zone.prototype.change = function(id) {
  * });
  */
 Zone.prototype.createChange = function(config, callback) {
-  var self = this;
+  const self = this;
 
   if (!config || (!config.add && !config.delete)) {
     throw new Error('Cannot create a change with no additions or deletions.');
   }
 
-  var body = extend(
+  const body = extend(
     {
       additions: groupByType(arrify(config.add).map(exec('toJSON'))),
       deletions: groupByType(arrify(config.delete).map(exec('toJSON'))),
@@ -358,14 +358,14 @@ Zone.prototype.createChange = function(config, callback) {
   function groupByType(changes) {
     changes = groupBy(changes, 'type');
 
-    var changesArray = [];
+    const changesArray = [];
 
-    for (var recordType in changes) {
-      var recordsByName = groupBy(changes[recordType], 'name');
+    for (const recordType in changes) {
+      const recordsByName = groupBy(changes[recordType], 'name');
 
-      for (var recordName in recordsByName) {
-        var records = recordsByName[recordName];
-        var templateRecord = extend({}, records[0]);
+      for (const recordName in recordsByName) {
+        const records = recordsByName[recordName];
+        const templateRecord = extend({}, records[0]);
 
         if (records.length > 1) {
           // Combine the `rrdatas` values from all records of the same type.
@@ -391,7 +391,7 @@ Zone.prototype.createChange = function(config, callback) {
         return;
       }
 
-      var change = self.change(resp.id);
+      const change = self.change(resp.id);
       change.metadata = resp;
 
       callback(null, change, resp);
@@ -593,7 +593,7 @@ Zone.prototype.deleteRecords = function(records, callback) {
  * @returns {Promise<ZoneEmptyResponse>}
  */
 Zone.prototype.empty = function(callback) {
-  var self = this;
+  const self = this;
 
   this.getRecords(function(err, records) {
     if (err) {
@@ -601,7 +601,7 @@ Zone.prototype.empty = function(callback) {
       return;
     }
 
-    var recordsToDelete = records.filter(function(record) {
+    const recordsToDelete = records.filter(function(record) {
       return record.type !== 'NS' && record.type !== 'SOA';
     });
 
@@ -656,7 +656,7 @@ Zone.prototype.export = function(localPath, callback) {
       return;
     }
 
-    var stringRecords = records.map(exec('toString')).join('\n');
+    const stringRecords = records.map(exec('toString')).join('\n');
 
     fs.writeFile(localPath, stringRecords, 'utf-8', function(err) {
       callback(err || null);
@@ -729,7 +729,7 @@ Zone.prototype.export = function(localPath, callback) {
  * });
  */
 Zone.prototype.getChanges = function(query, callback) {
-  var self = this;
+  const self = this;
 
   if (is.fn(query)) {
     callback = query;
@@ -752,13 +752,13 @@ Zone.prototype.getChanges = function(query, callback) {
         return;
       }
 
-      var changes = (resp.changes || []).map(function(change) {
-        var changeInstance = self.change(change.id);
+      const changes = (resp.changes || []).map(function(change) {
+        const changeInstance = self.change(change.id);
         changeInstance.metadata = change;
         return changeInstance;
       });
 
-      var nextQuery = null;
+      let nextQuery = null;
       if (resp.nextPageToken) {
         nextQuery = extend({}, query, {
           pageToken: resp.nextPageToken,
@@ -892,7 +892,7 @@ Zone.prototype.getChangesStream = common.paginator.streamify('getChanges');
  * });
  */
 Zone.prototype.getRecords = function(query, callback) {
-  var self = this;
+  const self = this;
 
   if (is.fn(query)) {
     callback = query;
@@ -900,7 +900,7 @@ Zone.prototype.getRecords = function(query, callback) {
   }
 
   if (is.string(query) || is.array(query)) {
-    var filterByTypes_ = {};
+    const filterByTypes_ = {};
 
     // For faster lookups, store the record types the user wants in an object.
     arrify(query).forEach(function(type) {
@@ -912,7 +912,7 @@ Zone.prototype.getRecords = function(query, callback) {
     };
   }
 
-  var requestQuery = extend({}, query);
+  const requestQuery = extend({}, query);
   delete requestQuery.filterByTypes_;
 
   this.request(
@@ -926,7 +926,7 @@ Zone.prototype.getRecords = function(query, callback) {
         return;
       }
 
-      var records = (resp.rrsets || []).map(function(record) {
+      let records = (resp.rrsets || []).map(function(record) {
         return self.record(record.type, record);
       });
 
@@ -936,7 +936,7 @@ Zone.prototype.getRecords = function(query, callback) {
         });
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
       if (resp.nextPageToken) {
         nextQuery = extend({}, query, {
           pageToken: resp.nextPageToken,
@@ -1023,7 +1023,7 @@ Zone.prototype.getRecordsStream = common.paginator.streamify('getRecords');
  * });
  */
 Zone.prototype.import = function(localPath, callback) {
-  var self = this;
+  const self = this;
 
   fs.readFile(localPath, 'utf-8', function(err, file) {
     if (err) {
@@ -1031,15 +1031,15 @@ Zone.prototype.import = function(localPath, callback) {
       return;
     }
 
-    var parsedZonefile = zonefile.parse(file);
-    var defaultTTL = parsedZonefile.$ttl;
+    const parsedZonefile = zonefile.parse(file);
+    const defaultTTL = parsedZonefile.$ttl;
     delete parsedZonefile.$ttl;
 
-    var recordTypes = Object.keys(parsedZonefile);
-    var recordsToCreate = [];
+    const recordTypes = Object.keys(parsedZonefile);
+    const recordsToCreate = [];
 
     recordTypes.forEach(function(recordType) {
-      var recordTypeSet = arrify(parsedZonefile[recordType]);
+      const recordTypeSet = arrify(parsedZonefile[recordType]);
 
       recordTypeSet.forEach(function(record) {
         record.ttl = record.ttl || defaultTTL;
@@ -1171,7 +1171,7 @@ Zone.prototype.record = function(type, metadata) {
  * });
  */
 Zone.prototype.replaceRecords = function(recordType, newRecords, callback) {
-  var self = this;
+  const self = this;
 
   this.getRecords(recordType, function(err, recordsToDelete) {
     if (err) {
@@ -1208,7 +1208,7 @@ Zone.prototype.replaceRecords = function(recordType, newRecords, callback) {
  * });
  */
 Zone.prototype.deleteRecordsByType_ = function(recordTypes, callback) {
-  var self = this;
+  const self = this;
 
   this.getRecords(recordTypes, function(err, records) {
     if (err) {
diff --git a/system-test/dns.js b/system-test/dns.js
index 34aa84c..f85b02c 100644
--- a/system-test/dns.js
+++ b/system-test/dns.js
@@ -16,18 +16,18 @@
 
 'use strict';
 
-var assert = require('assert');
-var async = require('async');
-var exec = require('methmeth');
-var format = require('string-format-obj');
-var fs = require('fs');
-var tmp = require('tmp');
-var uuid = require('uuid');
+const assert = require('assert');
+const async = require('async');
+const exec = require('methmeth');
+const format = require('string-format-obj');
+const fs = require('fs');
+const tmp = require('tmp');
+const uuid = require('uuid');
 
-var DNS = require('../');
+const DNS = require('../');
 
-var dns = new DNS();
-var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
+const dns = new DNS();
+const DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
 
 // Only run the tests if there is a domain to test with.
 (DNS_DOMAIN ? describe : describe.skip)('dns', function() {
@@ -36,10 +36,10 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
     return;
   }
 
-  var ZONE_NAME = 'test-zone-' + uuid.v4().substr(0, 18);
-  var ZONE = dns.zone(ZONE_NAME);
+  const ZONE_NAME = 'test-zone-' + uuid.v4().substr(0, 18);
+  const ZONE = dns.zone(ZONE_NAME);
 
-  var records = {
+  const records = {
     a: ZONE.record('a', {
       ttl: 86400,
       name: DNS_DOMAIN,
@@ -154,7 +154,7 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
     });
 
     it('should support all types of records', function(done) {
-      var recordsToCreate = [
+      const recordsToCreate = [
         records.a,
         records.aaaa,
         records.cname,
@@ -172,8 +172,8 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
     });
 
     it('should import records from a zone file', function(done) {
-      var zoneFilename = require.resolve('./data/zonefile.zone');
-      var zoneFileTemplate = fs.readFileSync(zoneFilename, 'utf-8');
+      const zoneFilename = require.resolve('./data/zonefile.zone');
+      let zoneFileTemplate = fs.readFileSync(zoneFilename, 'utf-8');
       zoneFileTemplate = format(zoneFileTemplate, {
         DNS_DOMAIN: DNS_DOMAIN,
       });
@@ -193,7 +193,7 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
             ZONE.getRecords(['spf', 'txt'], function(err, records) {
               assert.ifError(err);
 
-              var spfRecord = records.filter(function(record) {
+              const spfRecord = records.filter(function(record) {
                 return record.type === 'SPF';
               })[0];
 
@@ -202,7 +202,7 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
                 '"v=spf1" "mx:' + DNS_DOMAIN + '" "-all"'
               );
 
-              var txtRecord = records.filter(function(record) {
+              const txtRecord = records.filter(function(record) {
                 return record.type === 'TXT';
               })[0];
 
@@ -230,7 +230,7 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
             },
 
             function(next) {
-              var recordsToCreate = [records.spf, records.srv];
+              const recordsToCreate = [records.spf, records.srv];
 
               ZONE.addRecords(recordsToCreate, next);
             },
@@ -246,18 +246,18 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
 
     describe('changes', function() {
       it('should create a change', function(done) {
-        var record = ZONE.record('srv', {
+        const record = ZONE.record('srv', {
           ttl: 3600,
           name: DNS_DOMAIN,
           data: '10 0 5222 127.0.0.1.',
         });
 
-        var change = ZONE.change();
+        const change = ZONE.change();
 
         change.create({add: record}, function(err) {
           assert.ifError(err);
 
-          var addition = change.metadata.additions[0];
+          const addition = change.metadata.additions[0];
           delete addition.kind;
           assert.deepEqual(addition, record.toJSON());
 
@@ -277,8 +277,8 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
         ZONE.getChanges(function(err, changes) {
           assert.ifError(err);
 
-          var change = changes[0];
-          var expectedMetadata = change.metadata;
+          const change = changes[0];
+          const expectedMetadata = change.metadata;
 
           change.getMetadata(function(err, metadata) {
             assert.ifError(err);
@@ -304,7 +304,7 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
     });
 
     it('should cursor through records by type', function(done) {
-      var newRecords = [
+      const newRecords = [
         ZONE.record('cname', {
           ttl: 86400,
           name: '1.' + DNS_DOMAIN,
@@ -340,7 +340,7 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
     });
 
     it('should replace records', function(done) {
-      var name = 'test-zone-' + uuid.v4().substr(0, 18);
+      const name = 'test-zone-' + uuid.v4().substr(0, 18);
 
       // Do this in a new zone so no existing records are affected.
       dns.createZone(name, {dnsName: DNS_DOMAIN}, function(err, zone) {
@@ -349,9 +349,9 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
         zone.getRecords('ns', function(err, originalRecords) {
           assert.ifError(err);
 
-          var originalData = originalRecords[0].data;
+          const originalData = originalRecords[0].data;
 
-          var newRecord = zone.record('ns', {
+          const newRecord = zone.record('ns', {
             ttl: 3600,
             name: DNS_DOMAIN,
             data: ['ns1.nameserver.net.', 'ns2.nameserver.net.'],
@@ -360,8 +360,8 @@ var DNS_DOMAIN = process.env.GCLOUD_TESTS_DNS_DOMAIN;
           zone.replaceRecords('ns', newRecord, function(err, change) {
             assert.ifError(err);
 
-            var deleted = change.metadata.deletions[0].rrdatas;
-            var added = change.metadata.additions[0].rrdatas;
+            const deleted = change.metadata.deletions[0].rrdatas;
+            const added = change.metadata.additions[0].rrdatas;
 
             assert.deepEqual(deleted, originalData);
             assert.deepEqual(added, newRecord.data);
diff --git a/test/change.js b/test/change.js
index 3ba697d..2edf0f6 100644
--- a/test/change.js
+++ b/test/change.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+const assert = require('assert');
+const extend = require('extend');
+const nodeutil = require('util');
+const proxyquire = require('proxyquire');
+const ServiceObject = require('@google-cloud/common').ServiceObject;
+const util = require('@google-cloud/common').util;
+
+let promisified = false;
+const fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Change') {
       promisified = true;
@@ -40,15 +40,15 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Change', function() {
-  var Change;
-  var change;
+  let Change;
+  let change;
 
-  var ZONE = {
+  const ZONE = {
     name: 'zone-name',
     createChange: util.noop,
   };
 
-  var CHANGE_ID = 'change-id';
+  const CHANGE_ID = 'change-id';
 
   before(function() {
     Change = proxyquire('../src/change.js', {
@@ -67,7 +67,7 @@ describe('Change', function() {
     it('should inherit from ServiceObject', function() {
       assert(change instanceof ServiceObject);
 
-      var calledWith = change.calledWith_[0];
+      const calledWith = change.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, ZONE);
       assert.strictEqual(calledWith.baseUrl, '/changes');
@@ -86,7 +86,7 @@ describe('Change', function() {
 
   describe('change', function() {
     it('should call the parent change method', function(done) {
-      var config = {};
+      const config = {};
 
       change.parent.createChange = function(config_) {
         assert.strictEqual(config, config_);
@@ -97,8 +97,8 @@ describe('Change', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {};
+      const error = new Error('Error.');
+      const apiResponse = {};
 
       beforeEach(function() {
         change.parent.createChange = function(config, callback) {
@@ -118,11 +118,11 @@ describe('Change', function() {
     });
 
     describe('success', function() {
-      var changeInstance = {
+      const changeInstance = {
         id: 'id',
         metadata: {},
       };
-      var apiResponse = {};
+      const apiResponse = {};
 
       beforeEach(function() {
         change.parent.createChange = function(config, callback) {
diff --git a/test/index.js b/test/index.js
index 26c9e8d..7724907 100644
--- a/test/index.js
+++ b/test/index.js
@@ -16,16 +16,16 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var Service = require('@google-cloud/common').Service;
-var util = require('@google-cloud/common').util;
-
-var extended = false;
-var fakePaginator = {
+const arrify = require('arrify');
+const assert = require('assert');
+const extend = require('extend');
+const nodeutil = require('util');
+const proxyquire = require('proxyquire');
+const Service = require('@google-cloud/common').Service;
+const util = require('@google-cloud/common').util;
+
+let extended = false;
+const fakePaginator = {
   extend: function(Class, methods) {
     if (Class.name !== 'DNS') {
       return;
@@ -48,8 +48,8 @@ function FakeService() {
 
 nodeutil.inherits(FakeService, Service);
 
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let promisified = false;
+const fakeUtil = extend({}, util, {
   makeAuthenticatedRequestFactory: util.noop,
   promisifyAll: function(Class, options) {
     if (Class.name !== 'DNS') {
@@ -60,17 +60,17 @@ var fakeUtil = extend({}, util, {
     assert.deepEqual(options.exclude, ['zone']);
   },
 });
-var originalFakeUtil = extend(true, {}, fakeUtil);
+const originalFakeUtil = extend(true, {}, fakeUtil);
 
 function FakeZone() {
   this.calledWith_ = arguments;
 }
 
 describe('DNS', function() {
-  var DNS;
-  var dns;
+  let DNS;
+  let dns;
 
-  var PROJECT_ID = 'project-id';
+  const PROJECT_ID = 'project-id';
 
   before(function() {
     DNS = proxyquire('../', {
@@ -110,8 +110,8 @@ describe('DNS', function() {
     });
 
     it('should normalize the arguments', function() {
-      var normalizeArgumentsCalled = false;
-      var options = {};
+      let normalizeArgumentsCalled = false;
+      const options = {};
 
       fakeUtil.normalizeArguments = function(context, options_) {
         normalizeArgumentsCalled = true;
@@ -126,9 +126,9 @@ describe('DNS', function() {
     it('should inherit from Service', function() {
       assert(dns instanceof Service);
 
-      var calledWith = dns.calledWith_[0];
+      const calledWith = dns.calledWith_[0];
 
-      var baseUrl = 'https://www.googleapis.com/dns/v1';
+      const baseUrl = 'https://www.googleapis.com/dns/v1';
       assert.strictEqual(calledWith.baseUrl, baseUrl);
       assert.deepEqual(calledWith.scopes, [
         'https://www.googleapis.com/auth/ndev.clouddns.readwrite',
@@ -139,8 +139,8 @@ describe('DNS', function() {
   });
 
   describe('createZone', function() {
-    var zoneName = 'zone-name';
-    var config = {dnsName: 'dns-name'};
+    const zoneName = 'zone-name';
+    const config = {dnsName: 'dns-name'};
 
     it('should throw if a zone name is not provided', function() {
       assert.throws(function() {
@@ -159,7 +159,7 @@ describe('DNS', function() {
     });
 
     it('should use a provided description', function(done) {
-      var cfg = extend({}, config, {description: 'description'});
+      const cfg = extend({}, config, {description: 'description'});
 
       dns.request = function(reqOpts) {
         assert.strictEqual(reqOpts.json.description, cfg.description);
@@ -183,7 +183,7 @@ describe('DNS', function() {
         assert.strictEqual(reqOpts.method, 'POST');
         assert.strictEqual(reqOpts.uri, '/managedZones');
 
-        var expectedBody = extend({}, config, {
+        const expectedBody = extend({}, config, {
           name: zoneName,
           description: '',
         });
@@ -196,8 +196,8 @@ describe('DNS', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      const error = new Error('Error.');
+      const apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         dns.request = function(reqOpts, callback) {
@@ -216,8 +216,8 @@ describe('DNS', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {name: zoneName};
-      var zone = {};
+      const apiResponse = {name: zoneName};
+      const zone = {};
 
       beforeEach(function() {
         dns.request = function(reqOpts, callback) {
@@ -260,7 +260,7 @@ describe('DNS', function() {
 
   describe('getZones', function() {
     it('should make the correct request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      const query = {a: 'b', c: 'd'};
 
       dns.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/managedZones');
@@ -282,8 +282,8 @@ describe('DNS', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      const error = new Error('Error.');
+      const apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         dns.request = function(reqOpts, callback) {
@@ -304,8 +304,8 @@ describe('DNS', function() {
     });
 
     describe('success', function() {
-      var zone = {name: 'zone-1', a: 'b', c: 'd'};
-      var apiResponse = {managedZones: [zone]};
+      const zone = {name: 'zone-1', a: 'b', c: 'd'};
+      const apiResponse = {managedZones: [zone]};
 
       beforeEach(function() {
         dns.request = function(reqOpts, callback) {
@@ -328,12 +328,12 @@ describe('DNS', function() {
       });
 
       it('should set a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        const apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        const query = {a: 'b', c: 'd'};
+        const originalQuery = extend({}, query);
 
         dns.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -386,8 +386,8 @@ describe('DNS', function() {
     });
 
     it('should return a Zone', function() {
-      var newZoneName = 'new-zone-name';
-      var newZone = dns.zone(newZoneName);
+      const newZoneName = 'new-zone-name';
+      const newZone = dns.zone(newZoneName);
 
       assert(newZone instanceof FakeZone);
       assert.strictEqual(newZone.calledWith_[0], dns);
diff --git a/test/record.js b/test/record.js
index 55b514b..8ef97d0 100644
--- a/test/record.js
+++ b/test/record.js
@@ -16,13 +16,13 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var proxyquire = require('proxyquire');
-var util = require('@google-cloud/common').util;
+const assert = require('assert');
+const extend = require('extend');
+const proxyquire = require('proxyquire');
+const util = require('@google-cloud/common').util;
 
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let promisified = false;
+const fakeUtil = extend({}, util, {
   promisifyAll: function(Class, options) {
     if (Class.name !== 'Record') {
       return;
@@ -34,14 +34,14 @@ var fakeUtil = extend({}, util, {
 });
 
 describe('Record', function() {
-  var Record;
-  var record;
+  let Record;
+  let record;
 
-  var ZONE = {
+  const ZONE = {
     deleteRecords: util.noop,
   };
-  var TYPE = 'A';
-  var METADATA = {
+  const TYPE = 'A';
+  const METADATA = {
     name: 'name',
     data: [],
     ttl: 86400,
@@ -77,18 +77,18 @@ describe('Record', function() {
     });
 
     it('should assign the parsed metadata', function() {
-      var parsedMetadata = record.toJSON();
+      const parsedMetadata = record.toJSON();
       delete parsedMetadata.rrdatas;
 
-      for (var prop in parsedMetadata) {
+      for (const prop in parsedMetadata) {
         assert.strictEqual(record[prop], parsedMetadata[prop]);
       }
     });
 
     it('should re-assign rrdatas to data', function() {
-      var originalRrdatas = [];
+      const originalRrdatas = [];
 
-      var recordThatHadRrdatas = new Record(ZONE, TYPE, {
+      const recordThatHadRrdatas = new Record(ZONE, TYPE, {
         rrdatas: originalRrdatas,
       });
 
@@ -99,16 +99,16 @@ describe('Record', function() {
 
   describe('fromZoneRecord_', function() {
     describe('a', function() {
-      var aRecord = {
+      const aRecord = {
         ip: '0.0.0.0',
         name: 'name',
         ttl: 86400,
       };
 
-      var expectedData = aRecord.ip;
+      const expectedData = aRecord.ip;
 
       it('should parse an A record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'a', aRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'a', aRecord);
 
         assert.strictEqual(record.type, 'A');
         assert.deepEqual(record.metadata.data, expectedData);
@@ -118,16 +118,16 @@ describe('Record', function() {
     });
 
     describe('aaaa', function() {
-      var aaaaRecord = {
+      const aaaaRecord = {
         ip: '2607:f8b0:400a:801::1005',
         name: 'name',
         ttl: 86400,
       };
 
-      var expectedData = aaaaRecord.ip;
+      const expectedData = aaaaRecord.ip;
 
       it('should parse an AAAA record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'aaaa', aaaaRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'aaaa', aaaaRecord);
 
         assert.strictEqual(record.type, 'AAAA');
         assert.strictEqual(record.metadata.data, expectedData);
@@ -137,16 +137,16 @@ describe('Record', function() {
     });
 
     describe('cname', function() {
-      var cnameRecord = {
+      const cnameRecord = {
         alias: 'example.com.',
         name: 'name',
         ttl: 86400,
       };
 
-      var expectedData = cnameRecord.alias;
+      const expectedData = cnameRecord.alias;
 
       it('should parse a CNAME record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'cname', cnameRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'cname', cnameRecord);
 
         assert.strictEqual(record.type, 'CNAME');
         assert.strictEqual(record.metadata.data, expectedData);
@@ -156,17 +156,17 @@ describe('Record', function() {
     });
 
     describe('mx', function() {
-      var mxRecord = {
+      const mxRecord = {
         preference: 0,
         host: 'mail',
         name: 'name',
         ttl: 86400,
       };
 
-      var expectedData = mxRecord.preference + ' ' + mxRecord.host;
+      const expectedData = mxRecord.preference + ' ' + mxRecord.host;
 
       it('should parse an MX record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'mx', mxRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'mx', mxRecord);
 
         assert.strictEqual(record.type, 'MX');
         assert.strictEqual(record.metadata.data, expectedData);
@@ -176,16 +176,16 @@ describe('Record', function() {
     });
 
     describe('ns', function() {
-      var nsRecord = {
+      const nsRecord = {
         host: 'example.com',
         name: 'name',
         ttl: 86400,
       };
 
-      var expectedData = nsRecord.host;
+      const expectedData = nsRecord.host;
 
       it('should parse an NS record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'ns', nsRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'ns', nsRecord);
 
         assert.strictEqual(record.type, 'NS');
         assert.strictEqual(record.metadata.data, expectedData);
@@ -195,7 +195,7 @@ describe('Record', function() {
     });
 
     describe('soa', function() {
-      var soaRecord = {
+      const soaRecord = {
         mname: 'ns1.nameserver.net.',
         rname: 'hostmaster.mydomain.com.',
         serial: 86400,
@@ -207,7 +207,7 @@ describe('Record', function() {
         ttl: 86400,
       };
 
-      var expectedData = [
+      const expectedData = [
         soaRecord.mname,
         soaRecord.rname,
         soaRecord.serial,
@@ -218,7 +218,7 @@ describe('Record', function() {
       ].join(' ');
 
       it('should parse an SOA record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'soa', soaRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'soa', soaRecord);
 
         assert.strictEqual(record.type, 'SOA');
         assert.strictEqual(record.metadata.data, expectedData);
@@ -228,16 +228,16 @@ describe('Record', function() {
     });
 
     describe('spf', function() {
-      var spfRecord = {
+      const spfRecord = {
         data: '"v=spf1" "mx:example.com"',
         name: 'name',
         ttl: 86400,
       };
 
-      var expectedData = spfRecord.data;
+      const expectedData = spfRecord.data;
 
       it('should parse an SPF record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'spf', spfRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'spf', spfRecord);
 
         assert.strictEqual(record.type, 'SPF');
         assert.strictEqual(record.metadata.data, expectedData);
@@ -247,7 +247,7 @@ describe('Record', function() {
     });
 
     describe('srv', function() {
-      var srvRecord = {
+      const srvRecord = {
         priority: 10,
         weight: 0,
         port: 5222,
@@ -256,7 +256,7 @@ describe('Record', function() {
         ttl: 86400,
       };
 
-      var expectedData = [
+      const expectedData = [
         srvRecord.priority,
         srvRecord.weight,
         srvRecord.port,
@@ -264,7 +264,7 @@ describe('Record', function() {
       ].join(' ');
 
       it('should parse an SRV record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'srv', srvRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'srv', srvRecord);
 
         assert.strictEqual(record.type, 'SRV');
         assert.strictEqual(record.metadata.data, expectedData);
@@ -274,16 +274,16 @@ describe('Record', function() {
     });
 
     describe('txt', function() {
-      var txtRecord = {
+      const txtRecord = {
         txt: 'txt-record-txt',
         name: 'name',
         ttl: 86400,
       };
 
-      var expectedData = txtRecord.txt;
+      const expectedData = txtRecord.txt;
 
       it('should parse a TXT record', function() {
-        var record = Record.fromZoneRecord_(ZONE, 'txt', txtRecord);
+        const record = Record.fromZoneRecord_(ZONE, 'txt', txtRecord);
 
         assert.strictEqual(record.type, 'TXT');
         assert.strictEqual(record.metadata.data, expectedData);
@@ -306,7 +306,7 @@ describe('Record', function() {
 
   describe('toJSON', function() {
     it('should format the data for the API', function() {
-      var expectedRecord = extend({}, METADATA, {
+      const expectedRecord = extend({}, METADATA, {
         type: 'A',
         rrdatas: METADATA.data,
       });
@@ -318,7 +318,7 @@ describe('Record', function() {
 
   describe('toString', function() {
     it('should format the data for a zonefile', function() {
-      var jsonRecord = extend({}, METADATA, {
+      const jsonRecord = extend({}, METADATA, {
         type: TYPE,
         rrdatas: ['example.com.', 'example2.com.'],
       });
@@ -327,7 +327,7 @@ describe('Record', function() {
         return jsonRecord;
       };
 
-      var expectedRecordString = [
+      const expectedRecordString = [
         [
           jsonRecord.name,
           jsonRecord.ttl,
diff --git a/test/zone.js b/test/zone.js
index 3892f9b..7d3adf5 100644
--- a/test/zone.js
+++ b/test/zone.js
@@ -16,20 +16,19 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var assert = require('assert');
-var exec = require('methmeth');
-var extend = require('extend');
-var flatten = require('lodash.flatten');
-var nodeutil = require('util');
-var prop = require('propprop');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-var uuid = require('uuid');
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+const arrify = require('arrify');
+const assert = require('assert');
+const exec = require('methmeth');
+const extend = require('extend');
+const flatten = require('lodash.flatten');
+const nodeutil = require('util');
+const prop = require('propprop');
+const proxyquire = require('proxyquire');
+const {ServiceObject, util} = require('@google-cloud/common');
+const uuid = require('uuid');
+
+let promisified = false;
+const fakeUtil = extend({}, util, {
   promisifyAll: function(Class, options) {
     if (Class.name !== 'Zone') {
       return;
@@ -40,16 +39,16 @@ var fakeUtil = extend({}, util, {
   },
 });
 
-var parseOverride;
-var fakeDnsZonefile = {
+let parseOverride;
+const fakeDnsZonefile = {
   parse: function() {
     return (parseOverride || util.noop).apply(null, arguments);
   },
 };
 
-var writeFileOverride;
-var readFileOverride;
-var fakeFs = {
+let writeFileOverride;
+let readFileOverride;
+const fakeFs = {
   readFile: function() {
     return (readFileOverride || util.noop).apply(null, arguments);
   },
@@ -66,7 +65,7 @@ function FakeRecord() {
   this.calledWith_ = arguments;
 }
 FakeRecord.fromZoneRecord_ = function() {
-  var record = new FakeRecord();
+  const record = new FakeRecord();
   record.calledWith_ = arguments;
   return record;
 };
@@ -78,8 +77,8 @@ function FakeServiceObject() {
 
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
-var extended = false;
-var fakePaginator = {
+let extended = false;
+const fakePaginator = {
   extend: function(Class, methods) {
     if (Class.name !== 'Zone') {
       return;
@@ -96,13 +95,13 @@ var fakePaginator = {
 };
 
 describe('Zone', function() {
-  var Zone;
-  var zone;
+  let Zone;
+  let zone;
 
-  var DNS = {
+  const DNS = {
     createZone: util.noop,
   };
-  var ZONE_NAME = 'zone-name';
+  const ZONE_NAME = 'zone-name';
 
   before(function() {
     Zone = proxyquire('../src/zone.js', {
@@ -144,7 +143,7 @@ describe('Zone', function() {
     });
 
     it('should inherit from ServiceObject', function(done) {
-      var dnsInstance = extend({}, DNS, {
+      const dnsInstance = extend({}, DNS, {
         createZone: {
           bind: function(context) {
             assert.strictEqual(context, dnsInstance);
@@ -153,10 +152,10 @@ describe('Zone', function() {
         },
       });
 
-      var zone = new Zone(dnsInstance, ZONE_NAME);
+      const zone = new Zone(dnsInstance, ZONE_NAME);
       assert(zone instanceof ServiceObject);
 
-      var calledWith = zone.calledWith_[0];
+      const calledWith = zone.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, dnsInstance);
       assert.strictEqual(calledWith.baseUrl, '/managedZones');
@@ -172,7 +171,7 @@ describe('Zone', function() {
 
   describe('addRecords', function() {
     it('should create a change with additions', function(done) {
-      var records = ['a', 'b', 'c'];
+      const records = ['a', 'b', 'c'];
 
       zone.createChange = function(options, callback) {
         assert.strictEqual(options.add, records);
@@ -185,9 +184,9 @@ describe('Zone', function() {
 
   describe('change', function() {
     it('should return a Change object', function() {
-      var changeId = 'change-id';
+      const changeId = 'change-id';
 
-      var change = zone.change(changeId);
+      const change = zone.change(changeId);
 
       assert(change instanceof FakeChange);
       assert.strictEqual(change.calledWith_[0], zone);
@@ -220,9 +219,9 @@ describe('Zone', function() {
     });
 
     it('should parse and rename add to additions', function(done) {
-      var recordsToAdd = [generateRecord(), generateRecord()];
+      const recordsToAdd = [generateRecord(), generateRecord()];
 
-      var expectedAdditions = recordsToAdd.map(exec('toJSON'));
+      const expectedAdditions = recordsToAdd.map(exec('toJSON'));
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.json.add, undefined);
@@ -234,9 +233,9 @@ describe('Zone', function() {
     });
 
     it('should parse and rename delete to deletions', function(done) {
-      var recordsToDelete = [generateRecord(), generateRecord()];
+      const recordsToDelete = [generateRecord(), generateRecord()];
 
-      var expectedDeletions = recordsToDelete.map(exec('toJSON'));
+      const expectedDeletions = recordsToDelete.map(exec('toJSON'));
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.json.delete, undefined);
@@ -248,13 +247,13 @@ describe('Zone', function() {
     });
 
     it('should group changes by name and type', function(done) {
-      var recordsToAdd = [
+      const recordsToAdd = [
         generateRecord({name: 'name.com.', type: 'mx'}),
         generateRecord({name: 'name.com.', type: 'mx'}),
       ];
 
       zone.request = function(reqOpts) {
-        var expectedRRDatas = flatten(
+        const expectedRRDatas = flatten(
           recordsToAdd.map(exec('toJSON')).map(prop('rrdatas'))
         );
 
@@ -284,8 +283,8 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      const error = new Error('Error.');
+      const apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -303,7 +302,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {id: 1, a: 'b', c: 'd'};
+      const apiResponse = {id: 1, a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -312,7 +311,7 @@ describe('Zone', function() {
       });
 
       it('should execute callback with Change & API response', function(done) {
-        var change = {};
+        const change = {};
 
         zone.change = function(id) {
           assert.strictEqual(id, apiResponse.id);
@@ -368,7 +367,7 @@ describe('Zone', function() {
 
   describe('deleteRecords', function() {
     it('should delete records by type if a string is given', function(done) {
-      var recordsToDelete = 'ns';
+      const recordsToDelete = 'ns';
 
       zone.deleteRecordsByType_ = function(types, callback) {
         assert.deepEqual(types, [recordsToDelete]);
@@ -379,7 +378,7 @@ describe('Zone', function() {
     });
 
     it('should create a change if record objects given', function(done) {
-      var recordsToDelete = {a: 'b', c: 'd'};
+      const recordsToDelete = {a: 'b', c: 'd'};
 
       zone.createChange = function(options, callback) {
         assert.deepEqual(options.delete, [recordsToDelete]);
@@ -400,7 +399,7 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
+      const error = new Error('Error.');
 
       beforeEach(function() {
         zone.getRecords = function(callback) {
@@ -417,7 +416,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var records = [
+      const records = [
         {type: 'A'},
         {type: 'AAAA'},
         {type: 'CNAME'},
@@ -431,7 +430,7 @@ describe('Zone', function() {
         {type: 'TXT'},
       ];
 
-      var expectedRecordsToDelete = records.filter(function(record) {
+      const expectedRecordsToDelete = records.filter(function(record) {
         return record.type !== 'NS' && record.type !== 'SOA';
       });
 
@@ -461,9 +460,9 @@ describe('Zone', function() {
   });
 
   describe('export', function() {
-    var path = './zonefile';
+    const path = './zonefile';
 
-    var records = [
+    const records = [
       {
         toString: function() {
           return 'a';
@@ -486,7 +485,7 @@ describe('Zone', function() {
       },
     ];
 
-    var expectedZonefileContents = 'a\na\na\na';
+    const expectedZonefileContents = 'a\na\na\na';
 
     beforeEach(function() {
       zone.getRecords = function(callback) {
@@ -496,7 +495,7 @@ describe('Zone', function() {
 
     describe('get records', function() {
       describe('error', function() {
-        var error = new Error('Error.');
+        const error = new Error('Error.');
 
         it('should execute callback with error', function(done) {
           zone.getRecords = function(callback) {
@@ -535,7 +534,7 @@ describe('Zone', function() {
       });
 
       describe('error', function() {
-        var error = new Error('Error.');
+        const error = new Error('Error.');
 
         beforeEach(function() {
           writeFileOverride = function(path, content, encoding, callback) {
@@ -579,7 +578,7 @@ describe('Zone', function() {
     });
 
     it('should accept a sort', function(done) {
-      var query = {sort: 'desc'};
+      const query = {sort: 'desc'};
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.qs.sortOrder, 'descending');
@@ -592,7 +591,7 @@ describe('Zone', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      const query = {a: 'b', c: 'd'};
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/changes');
@@ -605,8 +604,8 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      const error = new Error('Error.');
+      const apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -624,7 +623,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      const apiResponse = {
         changes: [{id: 1}],
       };
 
@@ -635,11 +634,11 @@ describe('Zone', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        const nextPageToken = 'next-page-token';
+        const apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        const expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -657,7 +656,7 @@ describe('Zone', function() {
       });
 
       it('should execute callback with Changes & API response', function(done) {
-        var change = {};
+        const change = {};
 
         zone.change = function(id) {
           assert.strictEqual(id, apiResponse.changes[0].id);
@@ -680,8 +679,8 @@ describe('Zone', function() {
 
   describe('getRecords', function() {
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      const error = new Error('Error.');
+      const apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -706,7 +705,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      const apiResponse = {
         rrsets: [{type: 'NS'}],
       };
 
@@ -717,11 +716,11 @@ describe('Zone', function() {
       });
 
       it('should execute callback with nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        const nextPageToken = 'next-page-token';
+        const apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {pageToken: nextPageToken};
+        const expectedNextQuery = {pageToken: nextPageToken};
 
         zone.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -737,7 +736,7 @@ describe('Zone', function() {
       });
 
       it('should execute callback with Records & API response', function(done) {
-        var record = {};
+        const record = {};
 
         zone.record = function(type, recordObject) {
           assert.strictEqual(type, apiResponse.rrsets[0].type);
@@ -762,7 +761,7 @@ describe('Zone', function() {
 
       describe('filtering', function() {
         it('should accept a string type', function(done) {
-          var types = ['MX', 'CNAME'];
+          const types = ['MX', 'CNAME'];
 
           zone.getRecords(types, function(err, records) {
             assert.ifError(err);
@@ -774,7 +773,7 @@ describe('Zone', function() {
         });
 
         it('should accept an array of types', function(done) {
-          var type = 'MX';
+          const type = 'MX';
 
           zone.getRecords(type, function(err, records) {
             assert.ifError(err);
@@ -798,7 +797,7 @@ describe('Zone', function() {
   });
 
   describe('import', function() {
-    var path = './zonefile';
+    const path = './zonefile';
 
     it('should read from the file', function(done) {
       readFileOverride = function(path_, encoding) {
@@ -811,7 +810,7 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
+      const error = new Error('Error.');
 
       beforeEach(function() {
         readFileOverride = function(path, encoding, callback) {
@@ -828,8 +827,8 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var recordType = 'ns';
-      var parsedZonefile = {};
+      const recordType = 'ns';
+      let parsedZonefile = {};
 
       beforeEach(function() {
         parsedZonefile = {
@@ -849,11 +848,11 @@ describe('Zone', function() {
         zone.addRecords = function(recordsToCreate, callback) {
           assert.strictEqual(recordsToCreate.length, 1);
 
-          var recordToCreate = recordsToCreate[0];
+          const recordToCreate = recordsToCreate[0];
 
           assert(recordToCreate instanceof FakeRecord);
 
-          var args = recordToCreate.calledWith_;
+          const args = recordToCreate.calledWith_;
           assert.strictEqual(args[0], zone);
           assert.strictEqual(args[1], recordType);
           assert.strictEqual(args[2], parsedZonefile[recordType]);
@@ -865,17 +864,17 @@ describe('Zone', function() {
       });
 
       it('should use the default ttl', function(done) {
-        var defaultTTL = '90';
+        const defaultTTL = '90';
 
         parsedZonefile.$ttl = defaultTTL;
         parsedZonefile[recordType] = {};
         parsedZonefile.mx = {ttl: '180'};
 
         zone.addRecords = function(recordsToCreate) {
-          var record1 = recordsToCreate[0].calledWith_[2];
+          const record1 = recordsToCreate[0].calledWith_[2];
           assert.strictEqual(record1.ttl, defaultTTL);
 
-          var record2 = recordsToCreate[1].calledWith_[2];
+          const record2 = recordsToCreate[1].calledWith_[2];
           assert.strictEqual(record2.ttl, '180');
 
           done();
@@ -888,14 +887,14 @@ describe('Zone', function() {
 
   describe('record', function() {
     it('should return a Record object', function() {
-      var type = 'a';
-      var metadata = {a: 'b', c: 'd'};
+      const type = 'a';
+      const metadata = {a: 'b', c: 'd'};
 
-      var record = zone.record(type, metadata);
+      const record = zone.record(type, metadata);
 
       assert(record instanceof FakeRecord);
 
-      var args = record.calledWith_;
+      const args = record.calledWith_;
       assert.strictEqual(args[0], zone);
       assert.strictEqual(args[1], type);
       assert.strictEqual(args[2], metadata);
@@ -904,7 +903,7 @@ describe('Zone', function() {
 
   describe('replaceRecords', function() {
     it('should get records', function(done) {
-      var recordType = 'ns';
+      const recordType = 'ns';
 
       zone.getRecords = function(recordType_) {
         assert.strictEqual(recordType_, recordType);
@@ -915,7 +914,7 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
+      const error = new Error('Error.');
 
       beforeEach(function() {
         zone.getRecords = function(recordType, callback) {
@@ -932,13 +931,13 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var recordsToCreate = [
+      const recordsToCreate = [
         {a: 'b', c: 'd'},
         {a: 'b', c: 'd'},
         {a: 'b', c: 'd'},
       ];
 
-      var recordsToDelete = [
+      const recordsToDelete = [
         {a: 'b', c: 'd'},
         {a: 'b', c: 'd'},
         {a: 'b', c: 'd'},
@@ -965,7 +964,7 @@ describe('Zone', function() {
 
   describe('deleteRecordsByType_', function() {
     it('should get records', function(done) {
-      var recordType = 'ns';
+      const recordType = 'ns';
 
       zone.getRecords = function(recordType_) {
         assert.strictEqual(recordType_, recordType);
@@ -976,7 +975,7 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
+      const error = new Error('Error.');
 
       beforeEach(function() {
         zone.getRecords = function(recordType, callback) {
@@ -993,7 +992,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var recordsToDelete = [
+      const recordsToDelete = [
         {a: 'b', c: 'd'},
         {a: 'b', c: 'd'},
         {a: 'b', c: 'd'},