diff --git a/client/src/templates/Challenges/redux/execute-challenge-saga.js b/client/src/templates/Challenges/redux/execute-challenge-saga.js
index 8868e48420..45989a8a7f 100644
--- a/client/src/templates/Challenges/redux/execute-challenge-saga.js
+++ b/client/src/templates/Challenges/redux/execute-challenge-saga.js
@@ -34,10 +34,7 @@ import {
   runTestInTestFrame
 } from '../utils/frame.js';
 
-const testWorker = createWorker('test-evaluator');
-const testTimeout = 5000;
-
-function* ExecuteChallengeSaga() {
+export function* executeChallengeSaga() {
   const consoleProxy = yield channel();
   try {
     const { js, bonfire, backend } = challengeTypes;
@@ -46,6 +43,7 @@ function* ExecuteChallengeSaga() {
     yield put(initLogs());
     yield put(initConsole('// running tests'));
     yield fork(logToConsole, consoleProxy);
+    const proxyLogger = args => consoleProxy.put(args);
 
     const state = yield select();
 
@@ -53,13 +51,13 @@ function* ExecuteChallengeSaga() {
     switch (challengeType) {
       case js:
       case bonfire:
-        testResults = yield ExecuteJSChallengeSaga(state, consoleProxy);
+        testResults = yield executeJSChallengeSaga(state, proxyLogger);
         break;
       case backend:
-        testResults = yield ExecuteBackendChallengeSaga(state, consoleProxy);
+        testResults = yield executeBackendChallengeSaga(state, proxyLogger);
         break;
       default:
-        testResults = yield ExecuteDOMChallengeSaga(state, consoleProxy);
+        testResults = yield executeDOMChallengeSaga(state, proxyLogger);
     }
 
     yield put(updateTests(testResults));
@@ -78,72 +76,59 @@ function* logToConsole(channel) {
   });
 }
 
-function* ExecuteJSChallengeSaga(state, proxyLogger) {
+function* executeJSChallengeSaga(state, proxyLogger) {
   const { build, sources } = yield call(buildJSChallenge, state);
   const code = sources && 'index' in sources ? sources['index'] : '';
 
-  const log = args => proxyLogger.put(args);
-  testWorker.on('LOG', log);
+  const testWorker = createWorker('test-evaluator');
+  testWorker.on('LOG', proxyLogger);
 
   try {
-    return yield call(executeTests, (testString, testTimeout) =>
-      testWorker
-        .execute(
+    return yield call(executeTests, async(testString, testTimeout) => {
+      try {
+        return await testWorker.execute(
           { script: build + '\n' + testString, code, sources },
           testTimeout
-        )
-        .then(result => {
-          testWorker.killWorker();
-          return result;
-        })
-    );
+        );
+      } finally {
+        testWorker.killWorker();
+      }
+    });
   } finally {
-    testWorker.remove('LOG', log);
+    testWorker.remove('LOG', proxyLogger);
   }
 }
 
-function createTestFrame(state, ctx, proxyLogger) {
-  return new Promise(resolve => {
-    const frameTest = createTestFramer(document, state, resolve, proxyLogger);
-    frameTest(ctx);
-  });
+function createTestFrame(ctx, proxyLogger) {
+  return new Promise(resolve =>
+    createTestFramer(document, resolve, proxyLogger)(ctx)
+  );
 }
 
-function* ExecuteDOMChallengeSaga(state, proxyLogger) {
+function* executeDOMChallengeSaga(state, proxyLogger) {
   const ctx = yield call(buildDOMChallenge, state);
-
-  yield call(createTestFrame, state, ctx, proxyLogger);
+  yield call(createTestFrame, ctx, proxyLogger);
   // wait for a code execution on a "ready" event in jQuery challenges
   yield delay(100);
 
   return yield call(executeTests, (testString, testTimeout) =>
-    Promise.race([
-      runTestInTestFrame(document, testString),
-      new Promise((_, reject) =>
-        setTimeout(() => reject('timeout'), testTimeout)
-      )
-    ])
+    runTestInTestFrame(document, testString, testTimeout)
   );
 }
 
 // TODO: use a web worker
-function* ExecuteBackendChallengeSaga(state, proxyLogger) {
+function* executeBackendChallengeSaga(state, proxyLogger) {
   const ctx = yield call(buildBackendChallenge, state);
-
-  yield call(createTestFrame, state, ctx, proxyLogger);
+  yield call(createTestFrame, ctx, proxyLogger);
 
   return yield call(executeTests, (testString, testTimeout) =>
-    Promise.race([
-      runTestInTestFrame(document, testString),
-      new Promise((_, reject) =>
-        setTimeout(() => reject('timeout'), testTimeout)
-      )
-    ])
+    runTestInTestFrame(document, testString, testTimeout)
   );
 }
 
 function* executeTests(testRunner) {
   const tests = yield select(challengeTestsSelector);
+  const testTimeout = 5000;
   const testResults = [];
   for (const { text, testString } of tests) {
     const newTest = { text, testString };
@@ -180,8 +165,8 @@ function* updateMainSaga() {
       return;
     }
     const state = yield select();
-    const frameMain = yield call(createMainFramer, document, state);
     const ctx = yield call(buildDOMChallenge, state);
+    const frameMain = yield call(createMainFramer, document);
     yield call(frameMain, ctx);
   } catch (err) {
     console.error(err);
@@ -190,7 +175,7 @@ function* updateMainSaga() {
 
 export function createExecuteChallengeSaga(types) {
   return [
-    takeLatest(types.executeChallenge, ExecuteChallengeSaga),
+    takeLatest(types.executeChallenge, executeChallengeSaga),
     takeLatest(
       [
         types.updateFile,
diff --git a/client/src/templates/Challenges/utils/frame.js b/client/src/templates/Challenges/utils/frame.js
index c0aa72d0d7..3402a5e393 100644
--- a/client/src/templates/Challenges/utils/frame.js
+++ b/client/src/templates/Challenges/utils/frame.js
@@ -3,8 +3,6 @@ import { configure, shallow, mount } from 'enzyme';
 import Adapter16 from 'enzyme-adapter-react-16';
 import { setConfig } from 'react-hot-loader';
 
-import { isJSEnabledSelector } from '../redux';
-
 // we use two different frames to make them all essentially pure functions
 // main iframe is responsible rendering the preview and is where we proxy the
 // console.log
@@ -33,23 +31,24 @@ const createHeader = (id = mainId) => `
   </script>
 `;
 
-export const runTestInTestFrame = async function(document, test) {
+export const runTestInTestFrame = async function(document, test, timeout) {
   const { contentDocument: frame } = document.getElementById(testId);
   // Enable Stateless Functional Component. Otherwise, enzyme-adapter-react-16
   // does not work correctly.
   setConfig({ pureSFC: true });
-  const result = await frame.__runTest(test);
-  setConfig({ pureSFC: false });
-  return result;
+  try {
+    return await Promise.race([
+      new Promise((_, reject) => setTimeout(() => reject('timeout'), timeout)),
+      frame.__runTest(test)
+    ]);
+  } finally {
+    setConfig({ pureSFC: false });
+  }
 };
 
-const createFrame = (document, state, id) => ctx => {
-  const isJSEnabled = isJSEnabledSelector(state);
+const createFrame = (document, id) => ctx => {
   const frame = document.createElement('iframe');
   frame.id = id;
-  if (!isJSEnabled) {
-    frame.sandbox = 'allow-same-origin';
-  }
   return {
     ...ctx,
     element: frame
@@ -77,7 +76,7 @@ const mountFrame = document => ({ element, ...rest }) => {
 const buildProxyConsole = proxyLogger => ctx => {
   const oldLog = ctx.window.console.log.bind(ctx.window.console);
   ctx.window.console.log = function proxyConsole(...args) {
-    proxyLogger.put(args);
+    proxyLogger(args);
     return oldLog(...args);
   };
   return ctx;
@@ -111,16 +110,16 @@ const writeContentToFrame = ctx => {
   return ctx;
 };
 
-export const createMainFramer = (document, state) =>
+export const createMainFramer = document =>
   flow(
-    createFrame(document, state, mainId),
+    createFrame(document, mainId),
     mountFrame(document),
     writeContentToFrame
   );
 
-export const createTestFramer = (document, state, frameReady, proxyConsole) =>
+export const createTestFramer = (document, frameReady, proxyConsole) =>
   flow(
-    createFrame(document, state, testId),
+    createFrame(document, testId),
     mountFrame(document),
     writeTestDepsToDocument(frameReady),
     buildProxyConsole(proxyConsole),