diff --git a/.eslintrc.js b/.eslintrc.js
index 36ff570d9..3010f60d3 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -1,3 +1,3 @@
 module.exports = {
-    extends: ['scratch', 'scratch/node']
+    extends: ['scratch', 'scratch/node', 'scratch/es6']
 };
diff --git a/test/fixtures/attach-test-storage.js b/test/fixtures/attach-test-storage.js
index 5b3dae086..3e75f5967 100644
--- a/test/fixtures/attach-test-storage.js
+++ b/test/fixtures/attach-test-storage.js
@@ -1,15 +1,15 @@
-var ScratchStorage = require('scratch-storage');
+const ScratchStorage = require('scratch-storage');
 
-var ASSET_SERVER = 'https://cdn.assets.scratch.mit.edu/';
-var PROJECT_SERVER = 'https://cdn.projects.scratch.mit.edu/';
+const ASSET_SERVER = 'https://cdn.assets.scratch.mit.edu/';
+const PROJECT_SERVER = 'https://cdn.projects.scratch.mit.edu/';
 
 /**
  * @param {Asset} asset - calculate a URL for this asset.
  * @returns {string} a URL to download a project file.
  */
-var getProjectUrl = function (asset) {
-    var assetIdParts = asset.assetId.split('.');
-    var assetUrlParts = [PROJECT_SERVER, 'internalapi/project/', assetIdParts[0], '/get/'];
+const getProjectUrl = function (asset) {
+    const assetIdParts = asset.assetId.split('.');
+    const assetUrlParts = [PROJECT_SERVER, 'internalapi/project/', assetIdParts[0], '/get/'];
     if (assetIdParts[1]) {
         assetUrlParts.push(assetIdParts[1]);
     }
@@ -20,8 +20,8 @@ var getProjectUrl = function (asset) {
  * @param {Asset} asset - calculate a URL for this asset.
  * @returns {string} a URL to download a project asset (PNG, WAV, etc.)
  */
-var getAssetUrl = function (asset) {
-    var assetUrlParts = [
+const getAssetUrl = function (asset) {
+    const assetUrlParts = [
         ASSET_SERVER,
         'internalapi/asset/',
         asset.assetId,
@@ -36,9 +36,9 @@ var getAssetUrl = function (asset) {
  * Construct a new instance of ScratchStorage, provide it with default web sources, and attach it to the provided VM.
  * @param {VirtualMachine} vm - the VM which will own the new ScratchStorage instance.
  */
-var attachTestStorage = function (vm) {
-    var storage = new ScratchStorage();
-    var AssetType = storage.AssetType;
+const attachTestStorage = function (vm) {
+    const storage = new ScratchStorage();
+    const AssetType = storage.AssetType;
     storage.addWebSource([AssetType.Project], getProjectUrl);
     storage.addWebSource([AssetType.ImageVector, AssetType.ImageBitmap, AssetType.Sound], getAssetUrl);
     vm.attachStorage(storage);
diff --git a/test/fixtures/extract.js b/test/fixtures/extract.js
index fc33cf9ae..098261308 100644
--- a/test/fixtures/extract.js
+++ b/test/fixtures/extract.js
@@ -1,6 +1,6 @@
-var AdmZip = require('adm-zip');
+const AdmZip = require('adm-zip');
 
 module.exports = function (path) {
-    var zip = new AdmZip(path);
+    const zip = new AdmZip(path);
     return zip.readAsText('project.json', 'utf8');
 };
diff --git a/test/fixtures/fake-renderer.js b/test/fixtures/fake-renderer.js
index 2865b483a..a6cc9fc32 100644
--- a/test/fixtures/fake-renderer.js
+++ b/test/fixtures/fake-renderer.js
@@ -1,4 +1,4 @@
-var FakeRenderer = function () {
+const FakeRenderer = function () {
     this.unused = '';
     this.x = 0;
     this.y = 0;
diff --git a/test/integration/complex.js b/test/integration/complex.js
index b8777fe14..39bc0c667 100644
--- a/test/integration/complex.js
+++ b/test/integration/complex.js
@@ -1,32 +1,32 @@
-var fs = require('fs');
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const fs = require('fs');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var projectUri = path.resolve(__dirname, '../fixtures/complex.sb2');
-var project = extract(projectUri);
+const projectUri = path.resolve(__dirname, '../fixtures/complex.sb2');
+const project = extract(projectUri);
 
-var spriteUri = path.resolve(__dirname, '../fixtures/sprite.json');
-var sprite = fs.readFileSync(spriteUri, 'utf8');
+const spriteUri = path.resolve(__dirname, '../fixtures/sprite.json');
+const sprite = fs.readFileSync(spriteUri, 'utf8');
 
-test('complex', function (t) {
-    var vm = new VirtualMachine();
+test('complex', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length === 0);
         t.end();
         process.nextTick(process.exit);
     });
 
     // Manipulate each target
-    vm.on('targetsUpdate', function (data) {
-        var targets = data.targetList;
-        for (var i in targets) {
+    vm.on('targetsUpdate', data => {
+        const targets = data.targetList;
+        for (const i in targets) {
             if (targets[i].isStage === true) continue;
             if (targets[i].name.match(/test/)) continue;
 
@@ -55,12 +55,12 @@ test('complex', function (t) {
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // Post IO data
@@ -89,7 +89,7 @@ test('complex', function (t) {
             );
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/control.js b/test/integration/control.js
index 0d0dbfae7..4b65a0166 100644
--- a/test/integration/control.js
+++ b/test/integration/control.js
@@ -1,37 +1,37 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/control.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/control.sb2');
+const project = extract(uri);
 
-test('control', function (t) {
-    var vm = new VirtualMachine();
+test('control', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length > 0);
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
         });
     });
 
     // After two seconds, get playground data and stop
-    setTimeout(function () {
+    setTimeout(() => {
         vm.getPlaygroundData();
         vm.stopAll();
     }, 2000);
diff --git a/test/integration/data.js b/test/integration/data.js
index 52b528c5d..ba263fec1 100644
--- a/test/integration/data.js
+++ b/test/integration/data.js
@@ -1,34 +1,34 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/data.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/data.sb2');
+const project = extract(uri);
 
-test('data', function (t) {
-    var vm = new VirtualMachine();
+test('data', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function () {
+    vm.on('playgroundData', () => {
         // @todo Additional tests
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/event.js b/test/integration/event.js
index f404b2b58..34e21c63b 100644
--- a/test/integration/event.js
+++ b/test/integration/event.js
@@ -1,35 +1,35 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/event.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/event.sb2');
+const project = extract(uri);
 
-test('event', function (t) {
-    var vm = new VirtualMachine();
+test('event', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length > 0);
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/hat-execution-order.js b/test/integration/hat-execution-order.js
index 8a04d9428..44efcfa02 100644
--- a/test/integration/hat-execution-order.js
+++ b/test/integration/hat-execution-order.js
@@ -1,22 +1,22 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var projectUri = path.resolve(__dirname, '../fixtures/hat-execution-order.sb2');
-var project = extract(projectUri);
+const projectUri = path.resolve(__dirname, '../fixtures/hat-execution-order.sb2');
+const project = extract(projectUri);
 
-test('complex', function (t) {
-    var vm = new VirtualMachine();
+test('complex', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length === 0);
 
-        var results = vm.runtime.targets[0].lists.results.contents;
+        const results = vm.runtime.targets[0].lists.results.contents;
         t.deepEqual(results, ['3', '2', '1', 'stage']);
 
         t.end();
@@ -24,16 +24,16 @@ test('complex', function (t) {
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/import_sb2.js b/test/integration/import_sb2.js
index 010148cfd..547b645ea 100644
--- a/test/integration/import_sb2.js
+++ b/test/integration/import_sb2.js
@@ -1,26 +1,26 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
 
-var renderedTarget = require('../../src/sprites/rendered-target');
-var runtime = require('../../src/engine/runtime');
-var sb2 = require('../../src/import/sb2import');
+const renderedTarget = require('../../src/sprites/rendered-target');
+const runtime = require('../../src/engine/runtime');
+const sb2 = require('../../src/import/sb2import');
 
-test('spec', function (t) {
+test('spec', t => {
     t.type(sb2, 'function');
     t.end();
 });
 
-test('default', function (t) {
+test('default', t => {
     // Get SB2 JSON (string)
-    var uri = path.resolve(__dirname, '../fixtures/default.sb2');
-    var file = extract(uri);
+    const uri = path.resolve(__dirname, '../fixtures/default.sb2');
+    const file = extract(uri);
 
     // Create runtime instance & load SB2 into it
-    var rt = new runtime();
+    const rt = new runtime();
     attachTestStorage(rt);
-    sb2(file, rt).then(function (targets) {
+    sb2(file, rt).then(targets => {
         // Test
         t.type(file, 'string');
         t.type(rt, 'object');
diff --git a/test/integration/looks.js b/test/integration/looks.js
index 5f5313e9c..d251d4f85 100644
--- a/test/integration/looks.js
+++ b/test/integration/looks.js
@@ -1,35 +1,35 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/looks.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/looks.sb2');
+const project = extract(uri);
 
-test('looks', function (t) {
-    var vm = new VirtualMachine();
+test('looks', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length === 0);
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/motion.js b/test/integration/motion.js
index cbf0880e9..d8b1fc8d7 100644
--- a/test/integration/motion.js
+++ b/test/integration/motion.js
@@ -1,35 +1,35 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/motion.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/motion.sb2');
+const project = extract(uri);
 
-test('motion', function (t) {
-    var vm = new VirtualMachine();
+test('motion', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length > 0);
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/pen.js b/test/integration/pen.js
index fde8a52c4..f4da55fd1 100644
--- a/test/integration/pen.js
+++ b/test/integration/pen.js
@@ -1,34 +1,34 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/pen.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/pen.sb2');
+const project = extract(uri);
 
-test('pen', function (t) {
-    var vm = new VirtualMachine();
+test('pen', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function () {
+    vm.on('playgroundData', () => {
         // @todo Additional tests
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/procedure.js b/test/integration/procedure.js
index 177b24613..4abcf1e41 100644
--- a/test/integration/procedure.js
+++ b/test/integration/procedure.js
@@ -1,35 +1,35 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/procedure.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/procedure.sb2');
+const project = extract(uri);
 
-test('procedure', function (t) {
-    var vm = new VirtualMachine();
+test('procedure', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length === 0);
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/sensing.js b/test/integration/sensing.js
index f90d26d00..ca8fa1bb5 100644
--- a/test/integration/sensing.js
+++ b/test/integration/sensing.js
@@ -1,35 +1,35 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/sensing.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/sensing.sb2');
+const project = extract(uri);
 
-test('sensing', function (t) {
-    var vm = new VirtualMachine();
+test('sensing', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length > 0);
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/integration/sound.js b/test/integration/sound.js
index f1f46419a..7ab101593 100644
--- a/test/integration/sound.js
+++ b/test/integration/sound.js
@@ -1,35 +1,35 @@
-var path = require('path');
-var test = require('tap').test;
-var attachTestStorage = require('../fixtures/attach-test-storage');
-var extract = require('../fixtures/extract');
-var VirtualMachine = require('../../src/index');
+const path = require('path');
+const test = require('tap').test;
+const attachTestStorage = require('../fixtures/attach-test-storage');
+const extract = require('../fixtures/extract');
+const VirtualMachine = require('../../src/index');
 
-var uri = path.resolve(__dirname, '../fixtures/sound.sb2');
-var project = extract(uri);
+const uri = path.resolve(__dirname, '../fixtures/sound.sb2');
+const project = extract(uri);
 
-test('sound', function (t) {
-    var vm = new VirtualMachine();
+test('sound', t => {
+    const vm = new VirtualMachine();
     attachTestStorage(vm);
 
     // Evaluate playground data and exit
-    vm.on('playgroundData', function (e) {
-        var threads = JSON.parse(e.threads);
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
         t.ok(threads.length > 0);
         t.end();
         process.nextTick(process.exit);
     });
 
     // Start VM, load project, and run
-    t.doesNotThrow(function () {
+    t.doesNotThrow(() => {
         vm.start();
         vm.clear();
         vm.setCompatibilityMode(false);
         vm.setTurboMode(false);
-        vm.loadProject(project).then(function () {
+        vm.loadProject(project).then(() => {
             vm.greenFlag();
 
             // After two seconds, get playground data and stop
-            setTimeout(function () {
+            setTimeout(() => {
                 vm.getPlaygroundData();
                 vm.stopAll();
             }, 2000);
diff --git a/test/unit/blocks_control.js b/test/unit/blocks_control.js
index 7867524ce..ddb4d9f17 100644
--- a/test/unit/blocks_control.js
+++ b/test/unit/blocks_control.js
@@ -1,21 +1,21 @@
-var test = require('tap').test;
-var Control = require('../../src/blocks/scratch3_control');
-var Runtime = require('../../src/engine/runtime');
+const test = require('tap').test;
+const Control = require('../../src/blocks/scratch3_control');
+const Runtime = require('../../src/engine/runtime');
 
-test('getPrimitives', function (t) {
-    var rt = new Runtime();
-    var c = new Control(rt);
+test('getPrimitives', t => {
+    const rt = new Runtime();
+    const c = new Control(rt);
     t.type(c.getPrimitives(), 'object');
     t.end();
 });
 
-test('repeat', function (t) {
-    var rt = new Runtime();
-    var c = new Control(rt);
+test('repeat', t => {
+    const rt = new Runtime();
+    const c = new Control(rt);
 
     // Test harness (mocks `util`)
-    var i = 0;
-    var repeat = 10;
+    let i = 0;
+    const repeat = 10;
     var util = {
         stackFrame: Object.create(null),
         startBranch: function () {
@@ -31,13 +31,13 @@ test('repeat', function (t) {
     t.end();
 });
 
-test('repeatUntil', function (t) {
-    var rt = new Runtime();
-    var c = new Control(rt);
+test('repeatUntil', t => {
+    const rt = new Runtime();
+    const c = new Control(rt);
 
     // Test harness (mocks `util`)
-    var i = 0;
-    var repeat = 10;
+    let i = 0;
+    const repeat = 10;
     var util = {
         stackFrame: Object.create(null),
         startBranch: function () {
@@ -52,13 +52,13 @@ test('repeatUntil', function (t) {
     t.end();
 });
 
-test('forever', function (t) {
-    var rt = new Runtime();
-    var c = new Control(rt);
+test('forever', t => {
+    const rt = new Runtime();
+    const c = new Control(rt);
 
     // Test harness (mocks `util`)
-    var i = 0;
-    var util = {
+    let i = 0;
+    const util = {
         startBranch: function (branchNum, isLoop) {
             i++;
             t.strictEqual(branchNum, 1);
@@ -72,13 +72,13 @@ test('forever', function (t) {
     t.end();
 });
 
-test('if / ifElse', function (t) {
-    var rt = new Runtime();
-    var c = new Control(rt);
+test('if / ifElse', t => {
+    const rt = new Runtime();
+    const c = new Control(rt);
 
     // Test harness (mocks `util`)
-    var i = 0;
-    var util = {
+    let i = 0;
+    const util = {
         startBranch: function (branchNum) {
             i += branchNum;
         }
@@ -96,17 +96,17 @@ test('if / ifElse', function (t) {
     t.end();
 });
 
-test('stop', function (t) {
-    var rt = new Runtime();
-    var c = new Control(rt);
+test('stop', t => {
+    const rt = new Runtime();
+    const c = new Control(rt);
 
     // Test harness (mocks `util`)
-    var state = {
+    const state = {
         stopAll: 0,
         stopOtherTargetThreads: 0,
         stopThisScript: 0
     };
-    var util = {
+    const util = {
         stopAll: function () {
             state.stopAll++;
         },
diff --git a/test/unit/blocks_operators.js b/test/unit/blocks_operators.js
index dc4110d25..2caf71bca 100644
--- a/test/unit/blocks_operators.js
+++ b/test/unit/blocks_operators.js
@@ -1,129 +1,129 @@
-var test = require('tap').test;
-var Operators = require('../../src/blocks/scratch3_operators');
+const test = require('tap').test;
+const Operators = require('../../src/blocks/scratch3_operators');
 
-var blocks = new Operators(null);
+const blocks = new Operators(null);
 
-test('getPrimitives', function (t) {
+test('getPrimitives', t => {
     t.type(blocks.getPrimitives(), 'object');
     t.end();
 });
 
-test('add', function (t) {
+test('add', t => {
     t.strictEqual(blocks.add({NUM1: '1', NUM2: '1'}), 2);
     t.strictEqual(blocks.add({NUM1: 'foo', NUM2: 'bar'}), 0);
     t.end();
 });
 
-test('subtract', function (t) {
+test('subtract', t => {
     t.strictEqual(blocks.subtract({NUM1: '1', NUM2: '1'}), 0);
     t.strictEqual(blocks.subtract({NUM1: 'foo', NUM2: 'bar'}), 0);
     t.end();
 });
 
-test('multiply', function (t) {
+test('multiply', t => {
     t.strictEqual(blocks.multiply({NUM1: '2', NUM2: '2'}), 4);
     t.strictEqual(blocks.multiply({NUM1: 'foo', NUM2: 'bar'}), 0);
     t.end();
 });
 
-test('divide', function (t) {
+test('divide', t => {
     t.strictEqual(blocks.divide({NUM1: '2', NUM2: '2'}), 1);
     t.strictEqual(blocks.divide({NUM1: '1', NUM2: '0'}), Infinity);   // @todo
     t.ok(isNaN(blocks.divide({NUM1: 'foo', NUM2: 'bar'})));           // @todo
     t.end();
 });
 
-test('lt', function (t) {
+test('lt', t => {
     t.strictEqual(blocks.lt({OPERAND1: '1', OPERAND2: '2'}), true);
     t.strictEqual(blocks.lt({OPERAND1: '2', OPERAND2: '1'}), false);
     t.strictEqual(blocks.lt({OPERAND1: '1', OPERAND2: '1'}), false);
     t.end();
 });
 
-test('equals', function (t) {
+test('equals', t => {
     t.strictEqual(blocks.equals({OPERAND1: '1', OPERAND2: '2'}), false);
     t.strictEqual(blocks.equals({OPERAND1: '2', OPERAND2: '1'}), false);
     t.strictEqual(blocks.equals({OPERAND1: '1', OPERAND2: '1'}), true);
     t.end();
 });
 
-test('gt', function (t) {
+test('gt', t => {
     t.strictEqual(blocks.gt({OPERAND1: '1', OPERAND2: '2'}), false);
     t.strictEqual(blocks.gt({OPERAND1: '2', OPERAND2: '1'}), true);
     t.strictEqual(blocks.gt({OPERAND1: '1', OPERAND2: '1'}), false);
     t.end();
 });
 
-test('and', function (t) {
+test('and', t => {
     t.strictEqual(blocks.and({OPERAND1: true, OPERAND2: true}), true);
     t.strictEqual(blocks.and({OPERAND1: true, OPERAND2: false}), false);
     t.strictEqual(blocks.and({OPERAND1: false, OPERAND2: false}), false);
     t.end();
 });
 
-test('or', function (t) {
+test('or', t => {
     t.strictEqual(blocks.or({OPERAND1: true, OPERAND2: true}), true);
     t.strictEqual(blocks.or({OPERAND1: true, OPERAND2: false}), true);
     t.strictEqual(blocks.or({OPERAND1: false, OPERAND2: false}), false);
     t.end();
 });
 
-test('not', function (t) {
+test('not', t => {
     t.strictEqual(blocks.not({OPERAND: true}), false);
     t.strictEqual(blocks.not({OPERAND: false}), true);
     t.end();
 });
 
-test('random', function (t) {
-    var min = 0;
-    var max = 100;
-    var result = blocks.random({FROM: min, TO: max});
+test('random', t => {
+    const min = 0;
+    const max = 100;
+    const result = blocks.random({FROM: min, TO: max});
     t.ok(result >= min);
     t.ok(result <= max);
     t.end();
 });
 
-test('random - equal', function (t) {
-    var min = 1;
-    var max = 1;
+test('random - equal', t => {
+    const min = 1;
+    const max = 1;
     t.strictEqual(blocks.random({FROM: min, TO: max}), min);
     t.end();
 });
 
-test('random - decimal', function (t) {
-    var min = 0.1;
-    var max = 10;
-    var result = blocks.random({FROM: min, TO: max});
+test('random - decimal', t => {
+    const min = 0.1;
+    const max = 10;
+    const result = blocks.random({FROM: min, TO: max});
     t.ok(result >= min);
     t.ok(result <= max);
     t.end();
 });
 
-test('random - int', function (t) {
-    var min = 0;
-    var max = 10;
-    var result = blocks.random({FROM: min, TO: max});
+test('random - int', t => {
+    const min = 0;
+    const max = 10;
+    const result = blocks.random({FROM: min, TO: max});
     t.ok(result >= min);
     t.ok(result <= max);
     t.end();
 });
 
-test('random - reverse', function (t) {
-    var min = 0;
-    var max = 10;
-    var result = blocks.random({FROM: max, TO: min});
+test('random - reverse', t => {
+    const min = 0;
+    const max = 10;
+    const result = blocks.random({FROM: max, TO: min});
     t.ok(result >= min);
     t.ok(result <= max);
     t.end();
 });
 
-test('join', function (t) {
+test('join', t => {
     t.strictEqual(blocks.join({STRING1: 'foo', STRING2: 'bar'}), 'foobar');
     t.strictEqual(blocks.join({STRING1: '1', STRING2: '2'}), '12');
     t.end();
 });
 
-test('letterOf', function (t) {
+test('letterOf', t => {
     t.strictEqual(blocks.letterOf({STRING: 'foo', LETTER: 0}), '');
     t.strictEqual(blocks.letterOf({STRING: 'foo', LETTER: 1}), 'f');
     t.strictEqual(blocks.letterOf({STRING: 'foo', LETTER: 2}), 'o');
@@ -133,7 +133,7 @@ test('letterOf', function (t) {
     t.end();
 });
 
-test('length', function (t) {
+test('length', t => {
     t.strictEqual(blocks.length({STRING: ''}), 0);
     t.strictEqual(blocks.length({STRING: 'foo'}), 3);
     t.strictEqual(blocks.length({STRING: '1'}), 1);
@@ -141,21 +141,21 @@ test('length', function (t) {
     t.end();
 });
 
-test('mod', function (t) {
+test('mod', t => {
     t.strictEqual(blocks.mod({NUM1: 1, NUM2: 1}), 0);
     t.strictEqual(blocks.mod({NUM1: 3, NUM2: 6}), 3);
     t.strictEqual(blocks.mod({NUM1: -3, NUM2: 6}), 3);
     t.end();
 });
 
-test('round', function (t) {
+test('round', t => {
     t.strictEqual(blocks.round({NUM: 1}), 1);
     t.strictEqual(blocks.round({NUM: 1.1}), 1);
     t.strictEqual(blocks.round({NUM: 1.5}), 2);
     t.end();
 });
 
-test('mathop', function (t) {
+test('mathop', t => {
     t.strictEqual(blocks.mathop({OPERATOR: 'abs', NUM: -1}), 1);
     t.strictEqual(blocks.mathop({OPERATOR: 'floor', NUM: 1.5}), 1);
     t.strictEqual(blocks.mathop({OPERATOR: 'ceiling', NUM: 0.1}), 1);
diff --git a/test/unit/engine_adapter.js b/test/unit/engine_adapter.js
index 7c6cd2da1..37ad1ea39 100644
--- a/test/unit/engine_adapter.js
+++ b/test/unit/engine_adapter.js
@@ -1,22 +1,22 @@
-var test = require('tap').test;
-var adapter = require('../../src/engine/adapter');
-var events = require('../fixtures/events.json');
+const test = require('tap').test;
+const adapter = require('../../src/engine/adapter');
+const events = require('../fixtures/events.json');
 
-test('spec', function (t) {
+test('spec', t => {
     t.type(adapter, 'function');
     t.end();
 });
 
-test('invalid inputs', function (t) {
-    var nothing = adapter('not an object');
+test('invalid inputs', t => {
+    let nothing = adapter('not an object');
     t.type(nothing, 'undefined');
     nothing = adapter({noxmlproperty: true});
     t.type(nothing, 'undefined');
     t.end();
 });
 
-test('create event', function (t) {
-    var result = adapter(events.create);
+test('create event', t => {
+    const result = adapter(events.create);
 
     t.ok(Array.isArray(result));
     t.equal(result.length, 2);
@@ -43,8 +43,8 @@ test('create event', function (t) {
     t.end();
 });
 
-test('create with branch', function (t) {
-    var result = adapter(events.createbranch);
+test('create with branch', t => {
+    const result = adapter(events.createbranch);
     // Outer block
     t.type(result[0].id, 'string');
     t.type(result[0].opcode, 'string');
@@ -54,13 +54,13 @@ test('create with branch', function (t) {
     t.type(result[0].topLevel, 'boolean');
     t.equal(result[0].topLevel, true);
     // In branch
-    var branchBlockId = result[0].inputs.SUBSTACK.block;
-    var branchShadowId = result[0].inputs.SUBSTACK.shadow;
+    const branchBlockId = result[0].inputs.SUBSTACK.block;
+    const branchShadowId = result[0].inputs.SUBSTACK.shadow;
     t.type(branchBlockId, 'string');
     t.equal(branchShadowId, null);
     // Find actual branch block
-    var branchBlock = null;
-    for (var i = 0; i < result.length; i++) {
+    let branchBlock = null;
+    for (let i = 0; i < result.length; i++) {
         if (result[i].id === branchBlockId) {
             branchBlock = result[i];
         }
@@ -69,8 +69,8 @@ test('create with branch', function (t) {
     t.end();
 });
 
-test('create with two branches', function (t) {
-    var result = adapter(events.createtwobranches);
+test('create with two branches', t => {
+    const result = adapter(events.createtwobranches);
     // Outer block
     t.type(result[0].id, 'string');
     t.type(result[0].opcode, 'string');
@@ -81,18 +81,18 @@ test('create with two branches', function (t) {
     t.type(result[0].topLevel, 'boolean');
     t.equal(result[0].topLevel, true);
     // In branchs
-    var firstBranchBlockId = result[0].inputs.SUBSTACK.block;
-    var secondBranchBlockId = result[0].inputs.SUBSTACK2.block;
+    const firstBranchBlockId = result[0].inputs.SUBSTACK.block;
+    const secondBranchBlockId = result[0].inputs.SUBSTACK2.block;
     t.type(firstBranchBlockId, 'string');
     t.type(secondBranchBlockId, 'string');
-    var firstBranchShadowBlockId = result[0].inputs.SUBSTACK.shadow;
-    var secondBranchShadowBlockId = result[0].inputs.SUBSTACK2.shadow;
+    const firstBranchShadowBlockId = result[0].inputs.SUBSTACK.shadow;
+    const secondBranchShadowBlockId = result[0].inputs.SUBSTACK2.shadow;
     t.equal(firstBranchShadowBlockId, null);
     t.equal(secondBranchShadowBlockId, null);
     // Find actual branch blocks
-    var firstBranchBlock = null;
-    var secondBranchBlock = null;
-    for (var i = 0; i < result.length; i++) {
+    let firstBranchBlock = null;
+    let secondBranchBlock = null;
+    for (let i = 0; i < result.length; i++) {
         if (result[i].id === firstBranchBlockId) {
             firstBranchBlock = result[i];
         }
@@ -105,8 +105,8 @@ test('create with two branches', function (t) {
     t.end();
 });
 
-test('create with top-level shadow', function (t) {
-    var result = adapter(events.createtoplevelshadow);
+test('create with top-level shadow', t => {
+    const result = adapter(events.createtoplevelshadow);
     t.ok(Array.isArray(result));
     t.equal(result.length, 1);
 
@@ -120,8 +120,8 @@ test('create with top-level shadow', function (t) {
     t.end();
 });
 
-test('create with next connection', function (t) {
-    var result = adapter(events.createwithnext);
+test('create with next connection', t => {
+    const result = adapter(events.createwithnext);
 
     t.ok(Array.isArray(result));
     t.equal(result.length, 2);
@@ -148,21 +148,21 @@ test('create with next connection', function (t) {
     t.end();
 });
 
-test('create with obscured shadow', function (t) {
-    var result = adapter(events.createobscuredshadow);
+test('create with obscured shadow', t => {
+    const result = adapter(events.createobscuredshadow);
     t.ok(Array.isArray(result));
     t.equal(result.length, 4);
     t.end();
 });
 
-test('create with invalid block xml', function (t) {
+test('create with invalid block xml', t => {
     // Entirely invalid block XML
-    var result = adapter(events.createinvalid);
+    const result = adapter(events.createinvalid);
     t.ok(Array.isArray(result));
     t.equal(result.length, 0);
 
     // Invalid grandchild tag
-    var result2 = adapter(events.createinvalidgrandchild);
+    const result2 = adapter(events.createinvalidgrandchild);
     t.ok(Array.isArray(result2));
     t.equal(result2.length, 1);
     t.type(result2[0].id, 'string');
@@ -172,15 +172,15 @@ test('create with invalid block xml', function (t) {
     t.end();
 });
 
-test('create with invalid xml', function (t) {
-    var result = adapter(events.createbadxml);
+test('create with invalid xml', t => {
+    const result = adapter(events.createbadxml);
     t.ok(Array.isArray(result));
     t.equal(result.length, 0);
     t.end();
 });
 
-test('create with empty field', function (t) {
-    var result = adapter(events.createemptyfield);
+test('create with empty field', t => {
+    const result = adapter(events.createemptyfield);
     t.ok(Array.isArray(result));
     t.equal(result.length, 3);
     t.end();
diff --git a/test/unit/engine_blocks.js b/test/unit/engine_blocks.js
index cfb3cdd9c..1055cda68 100644
--- a/test/unit/engine_blocks.js
+++ b/test/unit/engine_blocks.js
@@ -1,8 +1,8 @@
-var test = require('tap').test;
-var Blocks = require('../../src/engine/blocks');
+const test = require('tap').test;
+const Blocks = require('../../src/engine/blocks');
 
-test('spec', function (t) {
-    var b = new Blocks();
+test('spec', t => {
+    const b = new Blocks();
 
     t.type(Blocks, 'function');
     t.type(b, 'object');
@@ -27,8 +27,8 @@ test('spec', function (t) {
 });
 
 // Getter tests
-test('getBlock', function (t) {
-    var b = new Blocks();
+test('getBlock', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -37,16 +37,16 @@ test('getBlock', function (t) {
         inputs: {},
         topLevel: true
     });
-    var block = b.getBlock('foo');
+    const block = b.getBlock('foo');
     t.type(block, 'object');
-    var notBlock = b.getBlock('?');
+    const notBlock = b.getBlock('?');
     t.type(notBlock, 'undefined');
     t.end();
 });
 
-test('getScripts', function (t) {
-    var b = new Blocks();
-    var scripts = b.getScripts();
+test('getScripts', t => {
+    const b = new Blocks();
+    let scripts = b.getScripts();
     t.type(scripts, 'object');
     t.equals(scripts.length, 0);
     // Create two top-level blocks and one not.
@@ -85,8 +85,8 @@ test('getScripts', function (t) {
 
 });
 
-test('getNextBlock', function (t) {
-    var b = new Blocks();
+test('getNextBlock', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -96,7 +96,7 @@ test('getNextBlock', function (t) {
         topLevel: true
     });
 
-    var next = b.getNextBlock('foo');
+    let next = b.getNextBlock('foo');
     t.equals(next, null);
 
     // Add a block with "foo" as its next.
@@ -113,14 +113,14 @@ test('getNextBlock', function (t) {
     t.equals(next, 'foo');
 
     // Block that doesn't exist.
-    var noBlock = b.getNextBlock('?');
+    const noBlock = b.getNextBlock('?');
     t.equals(noBlock, null);
 
     t.end();
 });
 
-test('getBranch', function (t) {
-    var b = new Blocks();
+test('getBranch', t => {
+    const b = new Blocks();
     // Single branch
     b.createBlock({
         id: 'foo',
@@ -145,17 +145,17 @@ test('getBranch', function (t) {
         topLevel: false
     });
 
-    var branch = b.getBranch('foo');
+    const branch = b.getBranch('foo');
     t.equals(branch, 'foo2');
 
-    var notBranch = b.getBranch('?');
+    const notBranch = b.getBranch('?');
     t.equals(notBranch, null);
 
     t.end();
 });
 
-test('getBranch2', function (t) {
-    var b = new Blocks();
+test('getBranch2', t => {
+    const b = new Blocks();
     // Second branch
     b.createBlock({
         id: 'foo',
@@ -193,16 +193,16 @@ test('getBranch2', function (t) {
         topLevel: false
     });
 
-    var branch1 = b.getBranch('foo', 1);
-    var branch2 = b.getBranch('foo', 2);
+    const branch1 = b.getBranch('foo', 1);
+    const branch2 = b.getBranch('foo', 2);
     t.equals(branch1, 'foo2');
     t.equals(branch2, 'foo3');
 
     t.end();
 });
 
-test('getBranch with none', function (t) {
-    var b = new Blocks();
+test('getBranch with none', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -211,14 +211,14 @@ test('getBranch with none', function (t) {
         inputs: {},
         topLevel: true
     });
-    var noBranch = b.getBranch('foo');
+    const noBranch = b.getBranch('foo');
     t.equals(noBranch, null);
     t.end();
 });
 
-test('getOpcode', function (t) {
-    var b = new Blocks();
-    var block = {
+test('getOpcode', t => {
+    const b = new Blocks();
+    const block = {
         id: 'foo',
         opcode: 'TEST_BLOCK',
         next: null,
@@ -227,17 +227,17 @@ test('getOpcode', function (t) {
         topLevel: true
     };
     b.createBlock(block);
-    var opcode = b.getOpcode(block);
+    const opcode = b.getOpcode(block);
     t.equals(opcode, 'TEST_BLOCK');
-    var undefinedBlock = b.getBlock('?');
-    var undefinedOpcode = b.getOpcode(undefinedBlock);
+    const undefinedBlock = b.getBlock('?');
+    const undefinedOpcode = b.getOpcode(undefinedBlock);
     t.equals(undefinedOpcode, null);
     t.end();
 });
 
 // Block events tests
-test('create', function (t) {
-    var b = new Blocks();
+test('create', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -253,8 +253,8 @@ test('create', function (t) {
     t.end();
 });
 
-test('move', function (t) {
-    var b = new Blocks();
+test('move', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -293,8 +293,8 @@ test('move', function (t) {
     t.end();
 });
 
-test('move into empty', function (t) {
-    var b = new Blocks();
+test('move into empty', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -320,8 +320,8 @@ test('move into empty', function (t) {
     t.end();
 });
 
-test('move no obscure shadow', function (t) {
-    var b = new Blocks();
+test('move no obscure shadow', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -354,8 +354,8 @@ test('move no obscure shadow', function (t) {
     t.end();
 });
 
-test('change', function (t) {
-    var b = new Blocks();
+test('change', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -411,8 +411,8 @@ test('change', function (t) {
     t.end();
 });
 
-test('delete', function (t) {
-    var b = new Blocks();
+test('delete', t => {
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -430,10 +430,10 @@ test('delete', function (t) {
     t.end();
 });
 
-test('delete chain', function (t) {
+test('delete chain', t => {
     // Create a chain of connected blocks and delete the top one.
     // All of them should be deleted.
-    var b = new Blocks();
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
@@ -470,10 +470,10 @@ test('delete chain', function (t) {
     t.end();
 });
 
-test('delete inputs', function (t) {
+test('delete inputs', t => {
     // Create a block with two inputs, one of which has its own input.
     // Delete the block - all of them should be deleted.
-    var b = new Blocks();
+    const b = new Blocks();
     b.createBlock({
         id: 'foo',
         opcode: 'TEST_BLOCK',
diff --git a/test/unit/engine_runtime.js b/test/unit/engine_runtime.js
index 40757c054..be431186d 100644
--- a/test/unit/engine_runtime.js
+++ b/test/unit/engine_runtime.js
@@ -1,8 +1,8 @@
-var test = require('tap').test;
-var Runtime = require('../../src/engine/runtime');
+const test = require('tap').test;
+const Runtime = require('../../src/engine/runtime');
 
-test('spec', function (t) {
-    var r = new Runtime();
+test('spec', t => {
+    const r = new Runtime();
 
     t.type(Runtime, 'function');
     t.type(r, 'object');
diff --git a/test/unit/engine_sequencer.js b/test/unit/engine_sequencer.js
index 1e000ad36..e5dcd0be7 100644
--- a/test/unit/engine_sequencer.js
+++ b/test/unit/engine_sequencer.js
@@ -1,15 +1,15 @@
-var test = require('tap').test;
-var Sequencer = require('../../src/engine/sequencer');
-var Runtime = require('../../src/engine/runtime');
-var Thread = require('../../src/engine/thread');
-var RenderedTarget = require('../../src/sprites/rendered-target');
-var Sprite = require('../../src/sprites/sprite');
+const test = require('tap').test;
+const Sequencer = require('../../src/engine/sequencer');
+const Runtime = require('../../src/engine/runtime');
+const Thread = require('../../src/engine/thread');
+const RenderedTarget = require('../../src/sprites/rendered-target');
+const Sprite = require('../../src/sprites/sprite');
 
-test('spec', function (t) {
+test('spec', t => {
     t.type(Sequencer, 'function');
     
-    var r = new Runtime();
-    var s = new Sequencer(r);
+    const r = new Runtime();
+    const s = new Sequencer(r);
 
     t.type(s, 'object');
     t.ok(s instanceof Sequencer);
@@ -23,13 +23,13 @@ test('spec', function (t) {
     t.end();
 });
 
-var randomString = function () {
-    var top = Math.random().toString(36);
+const randomString = function () {
+    const top = Math.random().toString(36);
     return top.substring(7);
 };
 
-var generateBlock = function (id) {
-    var block = {fields: Object,
+const generateBlock = function (id) {
+    const block = {fields: Object,
         id: id,
         inputs: {},
         STEPS: Object,
@@ -47,8 +47,8 @@ var generateBlock = function (id) {
     return block;
 };
 
-var generateBlockInput = function (id, next, inp) {
-    var block = {fields: Object,
+const generateBlockInput = function (id, next, inp) {
+    const block = {fields: Object,
         id: id,
         inputs: {SUBSTACK: {block: inp, name: 'SUBSTACK'}},
         STEPS: Object,
@@ -66,20 +66,20 @@ var generateBlockInput = function (id, next, inp) {
     return block;
 };
 
-var generateThread = function (runtime) {
-    var s = new Sprite();
-    var rt = new RenderedTarget(s, runtime);
-    var th = new Thread(randomString());
+const generateThread = function (runtime) {
+    const s = new Sprite();
+    const rt = new RenderedTarget(s, runtime);
+    const th = new Thread(randomString());
     
-    var next = randomString();
-    var inp = randomString();
-    var name = th.topBlock;
+    let next = randomString();
+    let inp = randomString();
+    let name = th.topBlock;
     
     rt.blocks.createBlock(generateBlockInput(name, next, inp));
     th.pushStack(name);
     rt.blocks.createBlock(generateBlock(inp));
     
-    for (var i = 0; i < 10; i++) {
+    for (let i = 0; i < 10; i++) {
         name = next;
         next = randomString();
         inp = randomString();
@@ -97,10 +97,10 @@ var generateThread = function (runtime) {
     return th;
 };
 
-test('stepThread', function (t) {
-    var r = new Runtime();
-    var s = new Sequencer(r);
-    var th = generateThread(r);
+test('stepThread', t => {
+    const r = new Runtime();
+    const s = new Sequencer(r);
+    let th = generateThread(r);
     t.notEquals(th.status, Thread.STATUS_DONE);
     s.stepThread(th);
     t.strictEquals(th.status, Thread.STATUS_DONE);
@@ -115,10 +115,10 @@ test('stepThread', function (t) {
     t.end();
 });
 
-test('stepToBranch', function (t) {
-    var r = new Runtime();
-    var s = new Sequencer(r);
-    var th = generateThread(r);
+test('stepToBranch', t => {
+    const r = new Runtime();
+    const s = new Sequencer(r);
+    const th = generateThread(r);
     s.stepToBranch(th, 2, false);
     t.strictEquals(th.peekStack(), null);
     th.popStack();
@@ -132,10 +132,10 @@ test('stepToBranch', function (t) {
     t.end();
 });
 
-test('retireThread', function (t) {
-    var r = new Runtime();
-    var s = new Sequencer(r);
-    var th = generateThread(r);
+test('retireThread', t => {
+    const r = new Runtime();
+    const s = new Sequencer(r);
+    const th = generateThread(r);
     t.strictEquals(th.stack.length, 12);
     s.retireThread(th);
     t.strictEquals(th.stack.length, 0);
@@ -144,11 +144,11 @@ test('retireThread', function (t) {
     t.end();
 });
 
-test('stepToProcedure', function (t) {
-    var r = new Runtime();
-    var s = new Sequencer(r);
-    var th = generateThread(r);
-    var expectedBlock = th.peekStack();
+test('stepToProcedure', t => {
+    const r = new Runtime();
+    const s = new Sequencer(r);
+    const th = generateThread(r);
+    let expectedBlock = th.peekStack();
     s.stepToProcedure(th, '');
     t.strictEquals(th.peekStack(), expectedBlock);
     s.stepToProcedure(th, 'faceCode');
@@ -163,10 +163,10 @@ test('stepToProcedure', function (t) {
     t.end();
 });
 
-test('stepThreads', function (t) {
-    var r = new Runtime();
+test('stepThreads', t => {
+    const r = new Runtime();
     r.currentStepTime = Infinity;
-    var s = new Sequencer(r);
+    const s = new Sequencer(r);
     t.strictEquals(s.stepThreads().length, 0);
     generateThread(r);
     t.strictEquals(r.threads.length, 1);
diff --git a/test/unit/engine_thread.js b/test/unit/engine_thread.js
index 815de5ca3..60419d360 100644
--- a/test/unit/engine_thread.js
+++ b/test/unit/engine_thread.js
@@ -1,12 +1,12 @@
-var test = require('tap').test;
-var Thread = require('../../src/engine/thread');
-var RenderedTarget = require('../../src/sprites/rendered-target');
-var Sprite = require('../../src/sprites/sprite');
+const test = require('tap').test;
+const Thread = require('../../src/engine/thread');
+const RenderedTarget = require('../../src/sprites/rendered-target');
+const Sprite = require('../../src/sprites/sprite');
 
-test('spec', function (t) {
+test('spec', t => {
     t.type(Thread, 'function');
     
-    var th = new Thread('arbitraryString');
+    const th = new Thread('arbitraryString');
     t.type(th, 'object');
     t.ok(th instanceof Thread);
     t.type(th.pushStack, 'function');
@@ -27,15 +27,15 @@ test('spec', function (t) {
     t.end();
 });
 
-test('pushStack', function (t) {
-    var th = new Thread('arbitraryString');
+test('pushStack', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     
     t.end();
 });
 
-test('popStack', function (t) {
-    var th = new Thread('arbitraryString');
+test('popStack', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     t.strictEquals(th.popStack(), 'arbitraryString');
     t.strictEquals(th.popStack(), undefined);
@@ -43,8 +43,8 @@ test('popStack', function (t) {
     t.end();
 });
 
-test('atStackTop', function (t) {
-    var th = new Thread('arbitraryString');
+test('atStackTop', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     th.pushStack('secondString');
     t.strictEquals(th.atStackTop(), false);
@@ -54,8 +54,8 @@ test('atStackTop', function (t) {
     t.end();
 });
 
-test('reuseStackForNextBlock', function (t) {
-    var th = new Thread('arbitraryString');
+test('reuseStackForNextBlock', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     th.reuseStackForNextBlock('secondString');
     t.strictEquals(th.popStack(), 'secondString');
@@ -63,8 +63,8 @@ test('reuseStackForNextBlock', function (t) {
     t.end();
 });
 
-test('peekStackFrame', function (t) {
-    var th = new Thread('arbitraryString');
+test('peekStackFrame', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     t.strictEquals(th.peekStackFrame().warpMode, false);
     th.popStack();
@@ -73,8 +73,8 @@ test('peekStackFrame', function (t) {
     t.end();
 });
 
-test('peekParentStackFrame', function (t) {
-    var th = new Thread('arbitraryString');
+test('peekParentStackFrame', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     th.peekStackFrame().warpMode = true;
     t.strictEquals(th.peekParentStackFrame(), null);
@@ -84,8 +84,8 @@ test('peekParentStackFrame', function (t) {
     t.end();
 });
 
-test('pushReportedValue', function (t) {
-    var th = new Thread('arbitraryString');
+test('pushReportedValue', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     th.pushStack('secondString');
     th.pushReportedValue('value');
@@ -94,8 +94,8 @@ test('pushReportedValue', function (t) {
     t.end();
 });
 
-test('peekStack', function (t) {
-    var th = new Thread('arbitraryString');
+test('peekStack', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     t.strictEquals(th.peekStack(), 'arbitraryString');
     th.popStack();
@@ -104,8 +104,8 @@ test('peekStack', function (t) {
     t.end();
 });
 
-test('PushGetParam', function (t) {
-    var th = new Thread('arbitraryString');
+test('PushGetParam', t => {
+    const th = new Thread('arbitraryString');
     th.pushStack('arbitraryString');
     th.pushParam('testParam', 'testValue');
     t.strictEquals(th.peekStackFrame().params.testParam, 'testValue');
@@ -114,11 +114,11 @@ test('PushGetParam', function (t) {
     t.end();
 });
 
-test('goToNextBlock', function (t) {
-    var th = new Thread('arbitraryString');
-    var s = new Sprite();
-    var rt = new RenderedTarget(s, null);
-    var block1 = {fields: Object,
+test('goToNextBlock', t => {
+    const th = new Thread('arbitraryString');
+    const s = new Sprite();
+    const rt = new RenderedTarget(s, null);
+    const block1 = {fields: Object,
         id: 'arbitraryString',
         inputs: Object,
         STEPS: Object,
@@ -132,7 +132,7 @@ test('goToNextBlock', function (t) {
         x: 0,
         y: 0
     };
-    var block2 = {fields: Object,
+    const block2 = {fields: Object,
         id: 'secondString',
         inputs: Object,
         STEPS: Object,
@@ -169,11 +169,11 @@ test('goToNextBlock', function (t) {
     t.end();
 });
 
-test('stopThisScript', function (t) {
-    var th = new Thread('arbitraryString');
-    var s = new Sprite();
-    var rt = new RenderedTarget(s, null);
-    var block1 = {fields: Object,
+test('stopThisScript', t => {
+    const th = new Thread('arbitraryString');
+    const s = new Sprite();
+    const rt = new RenderedTarget(s, null);
+    const block1 = {fields: Object,
         id: 'arbitraryString',
         inputs: Object,
         STEPS: Object,
@@ -187,7 +187,7 @@ test('stopThisScript', function (t) {
         x: 0,
         y: 0
     };
-    var block2 = {fields: Object,
+    const block2 = {fields: Object,
         id: 'secondString',
         inputs: Object,
         STEPS: Object,
@@ -221,11 +221,11 @@ test('stopThisScript', function (t) {
     t.end();
 });
 
-test('isRecursiveCall', function (t) {
-    var th = new Thread('arbitraryString');
-    var s = new Sprite();
-    var rt = new RenderedTarget(s, null);
-    var block1 = {fields: Object,
+test('isRecursiveCall', t => {
+    const th = new Thread('arbitraryString');
+    const s = new Sprite();
+    const rt = new RenderedTarget(s, null);
+    const block1 = {fields: Object,
         id: 'arbitraryString',
         inputs: Object,
         STEPS: Object,
@@ -239,7 +239,7 @@ test('isRecursiveCall', function (t) {
         x: 0,
         y: 0
     };
-    var block2 = {fields: Object,
+    const block2 = {fields: Object,
         id: 'secondString',
         inputs: Object,
         STEPS: Object,
diff --git a/test/unit/io_clock.js b/test/unit/io_clock.js
index 12989fcff..1978911e6 100644
--- a/test/unit/io_clock.js
+++ b/test/unit/io_clock.js
@@ -1,10 +1,10 @@
-var test = require('tap').test;
-var Clock = require('../../src/io/clock');
-var Runtime = require('../../src/engine/runtime');
+const test = require('tap').test;
+const Clock = require('../../src/io/clock');
+const Runtime = require('../../src/engine/runtime');
 
-test('spec', function (t) {
-    var rt = new Runtime();
-    var c = new Clock(rt);
+test('spec', t => {
+    const rt = new Runtime();
+    const c = new Clock(rt);
 
     t.type(Clock, 'function');
     t.type(c, 'object');
@@ -15,14 +15,14 @@ test('spec', function (t) {
     t.end();
 });
 
-test('cycle', function (t) {
-    var rt = new Runtime();
-    var c = new Clock(rt);
+test('cycle', t => {
+    const rt = new Runtime();
+    const c = new Clock(rt);
 
     t.ok(c.projectTimer() <= 0.1);
-    setTimeout(function () {
+    setTimeout(() => {
         c.resetProjectTimer();
-        setTimeout(function () {
+        setTimeout(() => {
             t.ok(c.projectTimer() > 0);
             c.pause();
             t.ok(c.projectTimer() > 0);
diff --git a/test/unit/io_keyboard.js b/test/unit/io_keyboard.js
index ad3a65c6d..a0a38f746 100644
--- a/test/unit/io_keyboard.js
+++ b/test/unit/io_keyboard.js
@@ -1,10 +1,10 @@
-var test = require('tap').test;
-var Keyboard = require('../../src/io/keyboard');
-var Runtime = require('../../src/engine/runtime');
+const test = require('tap').test;
+const Keyboard = require('../../src/io/keyboard');
+const Runtime = require('../../src/engine/runtime');
 
-test('spec', function (t) {
-    var rt = new Runtime();
-    var k = new Keyboard(rt);
+test('spec', t => {
+    const rt = new Runtime();
+    const k = new Keyboard(rt);
 
     t.type(k, 'object');
     t.type(k.postData, 'function');
@@ -12,9 +12,9 @@ test('spec', function (t) {
     t.end();
 });
 
-test('space', function (t) {
-    var rt = new Runtime();
-    var k = new Keyboard(rt);
+test('space', t => {
+    const rt = new Runtime();
+    const k = new Keyboard(rt);
 
     k.postData({
         keyCode: 32,
@@ -26,9 +26,9 @@ test('space', function (t) {
     t.end();
 });
 
-test('letter', function (t) {
-    var rt = new Runtime();
-    var k = new Keyboard(rt);
+test('letter', t => {
+    const rt = new Runtime();
+    const k = new Keyboard(rt);
 
     k.postData({
         keyCode: 65,
@@ -40,9 +40,9 @@ test('letter', function (t) {
     t.end();
 });
 
-test('number', function (t) {
-    var rt = new Runtime();
-    var k = new Keyboard(rt);
+test('number', t => {
+    const rt = new Runtime();
+    const k = new Keyboard(rt);
 
     k.postData({
         keyCode: 49,
@@ -54,9 +54,9 @@ test('number', function (t) {
     t.end();
 });
 
-test('keyup', function (t) {
-    var rt = new Runtime();
-    var k = new Keyboard(rt);
+test('keyup', t => {
+    const rt = new Runtime();
+    const k = new Keyboard(rt);
 
     k.postData({
         keyCode: 37,
diff --git a/test/unit/io_mouse.js b/test/unit/io_mouse.js
index ae4f3fe63..919786663 100644
--- a/test/unit/io_mouse.js
+++ b/test/unit/io_mouse.js
@@ -1,10 +1,10 @@
-var test = require('tap').test;
-var Mouse = require('../../src/io/mouse');
-var Runtime = require('../../src/engine/runtime');
+const test = require('tap').test;
+const Mouse = require('../../src/io/mouse');
+const Runtime = require('../../src/engine/runtime');
 
-test('spec', function (t) {
-    var rt = new Runtime();
-    var m = new Mouse(rt);
+test('spec', t => {
+    const rt = new Runtime();
+    const m = new Mouse(rt);
 
     t.type(m, 'object');
     t.type(m.postData, 'function');
@@ -14,9 +14,9 @@ test('spec', function (t) {
     t.end();
 });
 
-test('mouseUp', function (t) {
-    var rt = new Runtime();
-    var m = new Mouse(rt);
+test('mouseUp', t => {
+    const rt = new Runtime();
+    const m = new Mouse(rt);
 
     m.postData({
         x: 1,
@@ -31,9 +31,9 @@ test('mouseUp', function (t) {
     t.end();
 });
 
-test('mouseDown', function (t) {
-    var rt = new Runtime();
-    var m = new Mouse(rt);
+test('mouseDown', t => {
+    const rt = new Runtime();
+    const m = new Mouse(rt);
 
     m.postData({
         x: 10,
diff --git a/test/unit/spec.js b/test/unit/spec.js
index b16f181f0..7e2115567 100644
--- a/test/unit/spec.js
+++ b/test/unit/spec.js
@@ -1,8 +1,8 @@
-var test = require('tap').test;
-var VirtualMachine = require('../../src/index');
+const test = require('tap').test;
+const VirtualMachine = require('../../src/index');
 
-test('interface', function (t) {
-    var vm = new VirtualMachine();
+test('interface', t => {
+    const vm = new VirtualMachine();
     t.type(vm, 'object');
     t.type(vm.start, 'function');
     t.type(vm.greenFlag, 'function');
diff --git a/test/unit/sprites_rendered-target.js b/test/unit/sprites_rendered-target.js
index e22f364ba..3f8ee2c37 100644
--- a/test/unit/sprites_rendered-target.js
+++ b/test/unit/sprites_rendered-target.js
@@ -1,24 +1,24 @@
-var test = require('tap').test;
-var RenderedTarget = require('../../src/sprites/rendered-target');
-var Sprite = require('../../src/sprites/sprite');
-var Runtime = require('../../src/engine/runtime');
-var FakeRenderer = require('../fixtures/fake-renderer');
+const test = require('tap').test;
+const RenderedTarget = require('../../src/sprites/rendered-target');
+const Sprite = require('../../src/sprites/sprite');
+const Runtime = require('../../src/engine/runtime');
+const FakeRenderer = require('../fixtures/fake-renderer');
 
-test('clone effects', function (t) {
+test('clone effects', t => {
     // Create two clones and ensure they have different graphic effect objects.
     // Regression test for Github issue #224
-    var spr = new Sprite();
-    var a = new RenderedTarget(spr, null);
-    var b = new RenderedTarget(spr, null);
+    const spr = new Sprite();
+    const a = new RenderedTarget(spr, null);
+    const b = new RenderedTarget(spr, null);
     t.ok(a.effects !== b.effects);
     t.end();
 });
 
-test('setxy', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var a = new RenderedTarget(s, r);
-    var renderer = new FakeRenderer();
+test('setxy', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const a = new RenderedTarget(s, r);
+    const renderer = new FakeRenderer();
     a.renderer = renderer;
     a.setXY(123, 321, true);
     t.equals(a.x, 123);
@@ -26,54 +26,54 @@ test('setxy', function (t) {
     t.end();
 });
 
-test('direction', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var a = new RenderedTarget(s, r);
-    var renderer = new FakeRenderer();
+test('direction', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const a = new RenderedTarget(s, r);
+    const renderer = new FakeRenderer();
     a.renderer = renderer;
     a.setDirection(123);
     t.equals(a._getRenderedDirectionAndScale().direction, 123);
     t.end();
 });
 
-test('setSay', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var a = new RenderedTarget(s, r);
-    var renderer = new FakeRenderer();
+test('setSay', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const a = new RenderedTarget(s, r);
+    const renderer = new FakeRenderer();
     a.renderer = renderer;
     a.setSay();
     a.setSay('types not specified', 'message');
     t.end();
 });
 
-test('setVisible', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var a = new RenderedTarget(s, r);
-    var renderer = new FakeRenderer();
+test('setVisible', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const a = new RenderedTarget(s, r);
+    const renderer = new FakeRenderer();
     a.renderer = renderer;
     a.setVisible(true);
     t.end();
 });
 
-test('setSize', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var a = new RenderedTarget(s, r);
-    var renderer = new FakeRenderer();
+test('setSize', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const a = new RenderedTarget(s, r);
+    const renderer = new FakeRenderer();
     a.renderer = renderer;
     a.setSize(123);
     t.equals(a._getRenderedDirectionAndScale().scale[0], 123);
     t.end();
 });
 
-test('set and clear effects', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var a = new RenderedTarget(s, r);
-    var renderer = new FakeRenderer();
+test('set and clear effects', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const a = new RenderedTarget(s, r);
+    const renderer = new FakeRenderer();
     a.renderer = renderer;
     for (var effect in a.effects) {
         a.setEffect(effect, 1);
@@ -86,34 +86,34 @@ test('set and clear effects', function (t) {
     t.end();
 });
 
-test('setCostume', function (t) {
-    var o = new Object();
-    var s = new Sprite();
-    var r = new Runtime();
+test('setCostume', t => {
+    const o = new Object();
+    const s = new Sprite();
+    const r = new Runtime();
     s.costumes = [o];
-    var a = new RenderedTarget(s, r);
-    var renderer = new FakeRenderer();
+    const a = new RenderedTarget(s, r);
+    const renderer = new FakeRenderer();
     a.renderer = renderer;
     a.setCostume(0);
     t.end();
 });
 
-test('setRotationStyle', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var a = new RenderedTarget(s, r);
-    var renderer = new FakeRenderer();
+test('setRotationStyle', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const a = new RenderedTarget(s, r);
+    const renderer = new FakeRenderer();
     a.renderer = renderer;
     a.setRotationStyle(RenderedTarget.ROTATION_STYLE_NONE);
     t.end();
 });
 
-test('getBounds', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var renderer = new FakeRenderer();
+test('getBounds', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const renderer = new FakeRenderer();
     r.attachRenderer(renderer);
-    var a = new RenderedTarget(s, r);
+    const a = new RenderedTarget(s, r);
     a.renderer = renderer;
     t.equals(a.getBounds().top, 0);
     a.setXY(241, 241);
@@ -121,23 +121,23 @@ test('getBounds', function (t) {
     t.end();
 });
 
-test('isTouchingPoint', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var renderer = new FakeRenderer();
+test('isTouchingPoint', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const renderer = new FakeRenderer();
     r.attachRenderer(renderer);
-    var a = new RenderedTarget(s, r);
+    const a = new RenderedTarget(s, r);
     a.renderer = renderer;
     t.equals(a.isTouchingPoint(), true);
     t.end();
 });
 
-test('isTouchingEdge', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var renderer = new FakeRenderer();
+test('isTouchingEdge', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const renderer = new FakeRenderer();
     r.attachRenderer(renderer);
-    var a = new RenderedTarget(s, r);
+    const a = new RenderedTarget(s, r);
     a.renderer = renderer;
     t.equals(a.isTouchingEdge(), false);
     a.setXY(1000, 1000);
@@ -145,46 +145,46 @@ test('isTouchingEdge', function (t) {
     t.end();
 });
 
-test('isTouchingSprite', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var renderer = new FakeRenderer();
+test('isTouchingSprite', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const renderer = new FakeRenderer();
     r.attachRenderer(renderer);
-    var a = new RenderedTarget(s, r);
+    const a = new RenderedTarget(s, r);
     a.renderer = renderer;
     t.equals(a.isTouchingSprite('fake'), false);
     t.end();
 });
 
-test('isTouchingColor', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var renderer = new FakeRenderer();
+test('isTouchingColor', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const renderer = new FakeRenderer();
     r.attachRenderer(renderer);
-    var a = new RenderedTarget(s, r);
+    const a = new RenderedTarget(s, r);
     a.renderer = renderer;
     t.equals(a.isTouchingColor(), false);
     t.end();
 });
 
-test('colorIsTouchingColor', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var renderer = new FakeRenderer();
+test('colorIsTouchingColor', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const renderer = new FakeRenderer();
     r.attachRenderer(renderer);
-    var a = new RenderedTarget(s, r);
+    const a = new RenderedTarget(s, r);
     a.renderer = renderer;
     t.equals(a.colorIsTouchingColor(), false);
     t.end();
 });
 
-test('layers', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var renderer = new FakeRenderer();
-    var o = new Object();
+test('layers', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const renderer = new FakeRenderer();
+    const o = new Object();
     r.attachRenderer(renderer);
-    var a = new RenderedTarget(s, r);
+    const a = new RenderedTarget(s, r);
     a.renderer = renderer;
     a.goToFront();
     t.equals(a.renderer.order, 5);
@@ -196,12 +196,12 @@ test('layers', function (t) {
     t.end();
 });
 
-test('keepInFence', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var renderer = new FakeRenderer();
+test('keepInFence', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const renderer = new FakeRenderer();
     r.attachRenderer(renderer);
-    var a = new RenderedTarget(s, r);
+    const a = new RenderedTarget(s, r);
     a.renderer = renderer;
     t.equals(a.keepInFence(1000, 1000)[0], 240);
     t.equals(a.keepInFence(-1000, 1000)[0], -240);
@@ -210,40 +210,40 @@ test('keepInFence', function (t) {
     t.end();
 });
 
-test('#stopAll clears graphics effects', function (t) {
-    var s = new Sprite();
-    var r = new Runtime();
-    var a = new RenderedTarget(s, r);
-    var effectName = 'brightness';
+test('#stopAll clears graphics effects', t => {
+    const s = new Sprite();
+    const r = new Runtime();
+    const a = new RenderedTarget(s, r);
+    const effectName = 'brightness';
     a.setEffect(effectName, 100);
     a.onStopAll();
     t.equals(a.effects[effectName], 0);
     t.end();
 });
 
-test('#getCostumes returns the costumes', function (t) {
-    var spr = new Sprite();
-    var a = new RenderedTarget(spr, null);
-    var costumes = [1, 2, 3];
+test('#getCostumes returns the costumes', t => {
+    const spr = new Sprite();
+    const a = new RenderedTarget(spr, null);
+    const costumes = [1, 2, 3];
     a.sprite.costumes = costumes;
     t.equals(a.getCostumes(), costumes);
     t.end();
 });
 
-test('#getSounds returns the sounds', function (t) {
-    var spr = new Sprite();
-    var a = new RenderedTarget(spr, null);
-    var sounds = [1, 2, 3];
+test('#getSounds returns the sounds', t => {
+    const spr = new Sprite();
+    const a = new RenderedTarget(spr, null);
+    const sounds = [1, 2, 3];
     a.sprite.sounds = sounds;
     t.equals(a.getSounds(), sounds);
     t.end();
 });
 
-test('#toJSON returns the sounds and costumes', function (t) {
-    var spr = new Sprite();
-    var a = new RenderedTarget(spr, null);
-    var sounds = [1, 2, 3];
-    var costumes = ['a', 'b', 'c'];
+test('#toJSON returns the sounds and costumes', t => {
+    const spr = new Sprite();
+    const a = new RenderedTarget(spr, null);
+    const sounds = [1, 2, 3];
+    const costumes = ['a', 'b', 'c'];
     a.sprite.sounds = sounds;
     a.sprite.costumes = costumes;
     t.same(a.toJSON().sounds, sounds);
diff --git a/test/unit/util_cast.js b/test/unit/util_cast.js
index 861373bb2..8d30df368 100644
--- a/test/unit/util_cast.js
+++ b/test/unit/util_cast.js
@@ -1,7 +1,7 @@
-var test = require('tap').test;
-var cast = require('../../src/util/cast');
+const test = require('tap').test;
+const cast = require('../../src/util/cast');
 
-test('toNumber', function (t) {
+test('toNumber', t => {
     // Numeric
     t.strictEqual(cast.toNumber(0), 0);
     t.strictEqual(cast.toNumber(1), 1);
@@ -27,7 +27,7 @@ test('toNumber', function (t) {
     t.end();
 });
 
-test('toBoolean', function (t) {
+test('toBoolean', t => {
     // Numeric
     t.strictEqual(cast.toBoolean(0), false);
     t.strictEqual(cast.toBoolean(1), true);
@@ -50,7 +50,7 @@ test('toBoolean', function (t) {
     t.end();
 });
 
-test('toString', function (t) {
+test('toString', t => {
     // Numeric
     t.strictEqual(cast.toString(0), '0');
     t.strictEqual(cast.toString(1), '1');
@@ -73,7 +73,7 @@ test('toString', function (t) {
     t.end();
 });
 
-test('toRbgColorList', function (t) {
+test('toRbgColorList', t => {
     // Hex (minimal, see "color" util tests)
     t.deepEqual(cast.toRgbColorList('#000'), [0, 0, 0]);
     t.deepEqual(cast.toRgbColorList('#000000'), [0, 0, 0]);
@@ -91,7 +91,7 @@ test('toRbgColorList', function (t) {
     t.end();
 });
 
-test('toRbgColorObject', function (t) {
+test('toRbgColorObject', t => {
     // Hex (minimal, see "color" util tests)
     t.deepEqual(cast.toRgbColorObject('#000'), {r: 0, g: 0, b: 0});
     t.deepEqual(cast.toRgbColorObject('#000000'), {r: 0, g: 0, b: 0});
@@ -110,7 +110,7 @@ test('toRbgColorObject', function (t) {
     t.end();
 });
 
-test('compare', function (t) {
+test('compare', t => {
     // Numeric
     t.strictEqual(cast.compare(0, 0), 0);
     t.strictEqual(cast.compare(1, 0), 1);
@@ -137,7 +137,7 @@ test('compare', function (t) {
     t.end();
 });
 
-test('isInt', function (t) {
+test('isInt', t => {
     // Numeric
     t.strictEqual(cast.isInt(0), true);
     t.strictEqual(cast.isInt(1), true);
@@ -162,9 +162,9 @@ test('isInt', function (t) {
     t.end();
 });
 
-test('toListIndex', function (t) {
-    var list = [0, 1, 2, 3, 4, 5];
-    var empty = [];
+test('toListIndex', t => {
+    const list = [0, 1, 2, 3, 4, 5];
+    const empty = [];
 
     // Valid
     t.strictEqual(cast.toListIndex(1, list.length), 1);
@@ -184,13 +184,13 @@ test('toListIndex', function (t) {
     t.strictEqual(cast.toListIndex('last', empty.length), cast.LIST_INVALID);
 
     // "random"
-    var random = cast.toListIndex('random', list.length);
+    const random = cast.toListIndex('random', list.length);
     t.ok(random <= list.length);
     t.ok(random > 0);
     t.strictEqual(cast.toListIndex('random', empty.length), cast.LIST_INVALID);
 
     // "any" (alias for "random")
-    var any = cast.toListIndex('any', list.length);
+    const any = cast.toListIndex('any', list.length);
     t.ok(any <= list.length);
     t.ok(any > 0);
     t.strictEqual(cast.toListIndex('any', empty.length), cast.LIST_INVALID);
diff --git a/test/unit/util_color.js b/test/unit/util_color.js
index ea68b786d..61fc04a61 100644
--- a/test/unit/util_color.js
+++ b/test/unit/util_color.js
@@ -1,5 +1,5 @@
-var test = require('tap').test;
-var color = require('../../src/util/color');
+const test = require('tap').test;
+const color = require('../../src/util/color');
 
 /**
  * Assert that two HSV colors are similar to each other, within a tolerance.
@@ -7,7 +7,7 @@ var color = require('../../src/util/color');
  * @param {HSVObject} actual - the first HSV color to compare.
  * @param {HSVObject} expected - the other HSV color to compare.
  */
-var hsvSimilar = function (t, actual, expected) {
+const hsvSimilar = function (t, actual, expected) {
     if ((Math.abs(actual.h - expected.h) >= 1) ||
         (Math.abs(actual.s - expected.s) >= 0.01) ||
         (Math.abs(actual.v - expected.v) >= 0.01)
@@ -25,7 +25,7 @@ var hsvSimilar = function (t, actual, expected) {
  * @param {RGBObject} actual - the first RGB color to compare.
  * @param {RGBObject} expected - the other RGB color to compare.
  */
-var rgbSimilar = function (t, actual, expected) {
+const rgbSimilar = function (t, actual, expected) {
     if ((Math.abs(actual.r - expected.r) >= 1) ||
         (Math.abs(actual.g - expected.g) >= 1) ||
         (Math.abs(actual.b - expected.b) >= 1)
@@ -37,7 +37,7 @@ var rgbSimilar = function (t, actual, expected) {
     }
 };
 
-test('decimalToHex', function (t) {
+test('decimalToHex', t => {
     t.strictEqual(color.decimalToHex(0), '#000000');
     t.strictEqual(color.decimalToHex(1), '#000001');
     t.strictEqual(color.decimalToHex(16777215), '#ffffff');
@@ -46,7 +46,7 @@ test('decimalToHex', function (t) {
     t.end();
 });
 
-test('decimalToRgb', function (t) {
+test('decimalToRgb', t => {
     t.deepEqual(color.decimalToRgb(0), {a: 255, r: 0, g: 0, b: 0});
     t.deepEqual(color.decimalToRgb(1), {a: 255, r: 0, g: 0, b: 1});
     t.deepEqual(color.decimalToRgb(16777215), {a: 255, r: 255, g: 255, b: 255});
@@ -55,7 +55,7 @@ test('decimalToRgb', function (t) {
     t.end();
 });
 
-test('hexToRgb', function (t) {
+test('hexToRgb', t => {
     t.deepEqual(color.hexToRgb('#000'), {r: 0, g: 0, b: 0});
     t.deepEqual(color.hexToRgb('#000000'), {r: 0, g: 0, b: 0});
     t.deepEqual(color.hexToRgb('#fff'), {r: 255, g: 255, b: 255});
@@ -73,21 +73,21 @@ test('hexToRgb', function (t) {
     t.end();
 });
 
-test('rgbToHex', function (t) {
+test('rgbToHex', t => {
     t.strictEqual(color.rgbToHex({r: 0, g: 0, b: 0}), '#000000');
     t.strictEqual(color.rgbToHex({r: 255, g: 255, b: 255}), '#ffffff');
     t.strictEqual(color.rgbToHex({r: 0, g: 255, b: 170}), '#00ffaa');
     t.end();
 });
 
-test('rgbToDecimal', function (t) {
+test('rgbToDecimal', t => {
     t.strictEqual(color.rgbToDecimal({r: 0, g: 0, b: 0}), 0);
     t.strictEqual(color.rgbToDecimal({r: 255, g: 255, b: 255}), 16777215);
     t.strictEqual(color.rgbToDecimal({r: 0, g: 255, b: 170}), 65450);
     t.end();
 });
 
-test('hexToDecimal', function (t) {
+test('hexToDecimal', t => {
     t.strictEqual(color.hexToDecimal('#000'), 0);
     t.strictEqual(color.hexToDecimal('#000000'), 0);
     t.strictEqual(color.hexToDecimal('#fff'), 16777215);
@@ -97,7 +97,7 @@ test('hexToDecimal', function (t) {
     t.end();
 });
 
-test('hsvToRgb', function (t) {
+test('hsvToRgb', t => {
     rgbSimilar(t, color.hsvToRgb({h: 0, s: 0, v: 0}), {r: 0, g: 0, b: 0});
     rgbSimilar(t, color.hsvToRgb({h: 123, s: 0.1234, v: 0}), {r: 0, g: 0, b: 0});
     rgbSimilar(t, color.hsvToRgb({h: 0, s: 0, v: 1}), {r: 255, g: 255, b: 255});
@@ -108,7 +108,7 @@ test('hsvToRgb', function (t) {
     t.end();
 });
 
-test('rgbToHsv', function (t) {
+test('rgbToHsv', t => {
     hsvSimilar(t, color.rgbToHsv({r: 0, g: 0, b: 0}), {h: 0, s: 0, v: 0});
     hsvSimilar(t, color.rgbToHsv({r: 64, g: 64, b: 64}), {h: 0, s: 0, v: 0.25});
     hsvSimilar(t, color.rgbToHsv({r: 128, g: 128, b: 128}), {h: 0, s: 0, v: 0.5});
@@ -120,7 +120,7 @@ test('rgbToHsv', function (t) {
     t.end();
 });
 
-test('mixRgb', function (t) {
+test('mixRgb', t => {
     rgbSimilar(t, color.mixRgb({r: 10, g: 20, b: 30}, {r: 30, g: 40, b: 50}, -1), {r: 10, g: 20, b: 30});
     rgbSimilar(t, color.mixRgb({r: 10, g: 20, b: 30}, {r: 30, g: 40, b: 50}, 0), {r: 10, g: 20, b: 30});
     rgbSimilar(t, color.mixRgb({r: 10, g: 20, b: 30}, {r: 30, g: 40, b: 50}, 0.25), {r: 15, g: 25, b: 35});
diff --git a/test/unit/util_math.js b/test/unit/util_math.js
index 4c728dce1..d5a1c32fc 100644
--- a/test/unit/util_math.js
+++ b/test/unit/util_math.js
@@ -1,7 +1,7 @@
-var test = require('tap').test;
-var math = require('../../src/util/math-util');
+const test = require('tap').test;
+const math = require('../../src/util/math-util');
 
-test('degToRad', function (t) {
+test('degToRad', t => {
     t.strictEqual(math.degToRad(0), 0);
     t.strictEqual(math.degToRad(1), 0.017453292519943295);
     t.strictEqual(math.degToRad(180), Math.PI);
@@ -10,7 +10,7 @@ test('degToRad', function (t) {
     t.end();
 });
 
-test('radToDeg', function (t) {
+test('radToDeg', t => {
     t.strictEqual(math.radToDeg(0), 0);
     t.strictEqual(math.radToDeg(1), 57.29577951308232);
     t.strictEqual(math.radToDeg(180), 10313.240312354817);
@@ -19,7 +19,7 @@ test('radToDeg', function (t) {
     t.end();
 });
 
-test('clamp', function (t) {
+test('clamp', t => {
     t.strictEqual(math.clamp(0, 0, 10), 0);
     t.strictEqual(math.clamp(1, 0, 10), 1);
     t.strictEqual(math.clamp(-10, 0, 10), 0);
@@ -27,7 +27,7 @@ test('clamp', function (t) {
     t.end();
 });
 
-test('wrapClamp', function (t) {
+test('wrapClamp', t => {
     t.strictEqual(math.wrapClamp(0, 0, 10), 0);
     t.strictEqual(math.wrapClamp(1, 0, 10), 1);
     t.strictEqual(math.wrapClamp(-10, 0, 10), 1);
@@ -35,7 +35,7 @@ test('wrapClamp', function (t) {
     t.end();
 });
 
-test('tan', function (t) {
+test('tan', t => {
     t.strictEqual(math.tan(90), Infinity);
     t.strictEqual(math.tan(180), 0);
     t.strictEqual(math.tan(-90), -Infinity);
diff --git a/test/unit/util_string.js b/test/unit/util_string.js
index fdcd439d3..741336258 100644
--- a/test/unit/util_string.js
+++ b/test/unit/util_string.js
@@ -1,7 +1,7 @@
-var test = require('tap').test;
-var StringUtil = require('../../src/util/string-util');
+const test = require('tap').test;
+const StringUtil = require('../../src/util/string-util');
 
-test('withoutTrailingDigits', function (t) {
+test('withoutTrailingDigits', t => {
     t.strictEqual(StringUtil.withoutTrailingDigits('boeing747'), 'boeing');
     t.strictEqual(StringUtil.withoutTrailingDigits('boeing747 '), 'boeing747 ');
     t.strictEqual(StringUtil.withoutTrailingDigits('boeing𝟨'), 'boeing𝟨');
@@ -10,7 +10,7 @@ test('withoutTrailingDigits', function (t) {
     t.end();
 });
 
-test('unusedName', function (t) {
+test('unusedName', t => {
     t.strictEqual(
         StringUtil.unusedName(
             'name',
diff --git a/test/unit/util_timer.js b/test/unit/util_timer.js
index 4780ec44a..5c0f21790 100644
--- a/test/unit/util_timer.js
+++ b/test/unit/util_timer.js
@@ -1,8 +1,8 @@
-var test = require('tap').test;
-var Timer = require('../../src/util/timer');
+const test = require('tap').test;
+const Timer = require('../../src/util/timer');
 
-test('spec', function (t) {
-    var timer = new Timer();
+test('spec', t => {
+    const timer = new Timer();
 
     t.type(Timer, 'function');
     t.type(timer, 'object');
@@ -15,25 +15,25 @@ test('spec', function (t) {
     t.end();
 });
 
-test('time', function (t) {
-    var timer = new Timer();
-    var time = timer.time();
+test('time', t => {
+    const timer = new Timer();
+    const time = timer.time();
 
     t.ok(Date.now() >= time);
     t.end();
 });
 
-test('start / timeElapsed', function (t) {
-    var timer = new Timer();
-    var delay = 100;
-    var threshold = 1000 / 60;  // 60 hz
+test('start / timeElapsed', t => {
+    const timer = new Timer();
+    const delay = 100;
+    const threshold = 1000 / 60;  // 60 hz
 
     // Start timer
     timer.start();
 
     // Wait and measure timer
-    setTimeout(function () {
-        var timeElapsed = timer.timeElapsed();
+    setTimeout(() => {
+        const timeElapsed = timer.timeElapsed();
         t.ok(timeElapsed >= 0);
         t.ok(timeElapsed >= (delay - threshold) &&
              timeElapsed <= (delay + threshold));
diff --git a/test/unit/util_xml.js b/test/unit/util_xml.js
index 1906a2ab6..d22f37b61 100644
--- a/test/unit/util_xml.js
+++ b/test/unit/util_xml.js
@@ -1,9 +1,9 @@
-var test = require('tap').test;
-var xml = require('../../src/util/xml-escape');
+const test = require('tap').test;
+const xml = require('../../src/util/xml-escape');
 
-test('escape', function (t) {
-    var input = '<foo bar="he & llo \'"></foo>';
-    var output = '&lt;foo bar=&quot;he &amp; llo &apos;&quot;&gt;&lt;/foo&gt;';
+test('escape', t => {
+    const input = '<foo bar="he & llo \'"></foo>';
+    const output = '&lt;foo bar=&quot;he &amp; llo &apos;&quot;&gt;&lt;/foo&gt;';
     t.strictEqual(xml(input), output);
     t.end();
 });
diff --git a/test/unit/virtual-machine.js b/test/unit/virtual-machine.js
index eed537dd3..73cefb8a2 100644
--- a/test/unit/virtual-machine.js
+++ b/test/unit/virtual-machine.js
@@ -1,8 +1,8 @@
-var test = require('tap').test;
-var VirtualMachine = require('../../src/virtual-machine.js');
+const test = require('tap').test;
+const VirtualMachine = require('../../src/virtual-machine.js');
 
-test('renameSprite throws when there is no sprite with that id', function (t) {
-    var vm = new VirtualMachine();
+test('renameSprite throws when there is no sprite with that id', t => {
+    const vm = new VirtualMachine();
     vm.runtime.getTargetById = () => null;
     t.throws(
         (() => vm.renameSprite('id', 'name')),
@@ -11,9 +11,9 @@ test('renameSprite throws when there is no sprite with that id', function (t) {
     t.end();
 });
 
-test('renameSprite throws when used on a non-sprite target', function (t) {
-    var vm = new VirtualMachine();
-    var fakeTarget = {
+test('renameSprite throws when used on a non-sprite target', t => {
+    const vm = new VirtualMachine();
+    const fakeTarget = {
         isSprite: () => false
     };
     vm.runtime.getTargetById = () => (fakeTarget);
@@ -24,9 +24,9 @@ test('renameSprite throws when used on a non-sprite target', function (t) {
     t.end();
 });
 
-test('renameSprite throws when there is no sprite for given target', function (t) {
-    var vm = new VirtualMachine();
-    var fakeTarget = {
+test('renameSprite throws when there is no sprite for given target', t => {
+    const vm = new VirtualMachine();
+    const fakeTarget = {
         sprite: null,
         isSprite: () => true
     };
@@ -38,9 +38,9 @@ test('renameSprite throws when there is no sprite for given target', function (t
     t.end();
 });
 
-test('renameSprite sets the sprite name', function (t) {
-    var vm = new VirtualMachine();
-    var fakeTarget = {
+test('renameSprite sets the sprite name', t => {
+    const vm = new VirtualMachine();
+    const fakeTarget = {
         sprite: {name: 'original'},
         isSprite: () => true
     };
@@ -50,9 +50,9 @@ test('renameSprite sets the sprite name', function (t) {
     t.end();
 });
 
-test('renameSprite does not set sprite names to an empty string', function (t) {
-    var vm = new VirtualMachine();
-    var fakeTarget = {
+test('renameSprite does not set sprite names to an empty string', t => {
+    const vm = new VirtualMachine();
+    const fakeTarget = {
         sprite: {name: 'original'},
         isSprite: () => true
     };
@@ -62,9 +62,9 @@ test('renameSprite does not set sprite names to an empty string', function (t) {
     t.end();
 });
 
-test('renameSprite does not set sprite names to reserved names', function (t) {
-    var vm = new VirtualMachine();
-    var fakeTarget = {
+test('renameSprite does not set sprite names to reserved names', t => {
+    const vm = new VirtualMachine();
+    const fakeTarget = {
         sprite: {name: 'original'},
         isSprite: () => true
     };
@@ -74,8 +74,8 @@ test('renameSprite does not set sprite names to reserved names', function (t) {
     t.end();
 });
 
-test('renameSprite increments from existing sprite names', function (t) {
-    var vm = new VirtualMachine();
+test('renameSprite increments from existing sprite names', t => {
+    const vm = new VirtualMachine();
     vm.emitTargetsUpdate = () => {};
     vm.runtime.targets = [{
         id: 'id1',
diff --git a/webpack.config.js b/webpack.config.js
index b014e88ce..571256800 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -1,9 +1,9 @@
-var CopyWebpackPlugin = require('copy-webpack-plugin');
-var defaultsDeep = require('lodash.defaultsdeep');
-var path = require('path');
-var webpack = require('webpack');
+const CopyWebpackPlugin = require('copy-webpack-plugin');
+const defaultsDeep = require('lodash.defaultsdeep');
+const path = require('path');
+const webpack = require('webpack');
 
-var base = {
+const base = {
     devServer: {
         contentBase: false,
         host: '0.0.0.0',