diff --git a/package.json b/package.json
index c751f6d..2e29a90 100644
--- a/package.json
+++ b/package.json
@@ -36,34 +36,29 @@
     "eslint-config-google": "^0.7.1",
     "express": "^4.14.0",
     "firebase": "^3.5.1",
-    "geckodriver": "^1.3.0",
+    "geckodriver": "^1.6.0",
     "glob": "^7.1.1",
     "istanbul": "^0.4.5",
     "jsdoc": "^3.4.1",
     "mocha": "^3.1.2",
     "operadriver": "^1.0.0",
     "proxyquire": "^1.7.10",
-    "sinon": "^1.17.6"
+    "sinon": "^2.1.0"
   },
   "dependencies": {
     "chalk": "^1.1.3",
     "del": "^2.2.0",
     "dmg": "^0.1.0",
-    "fs-extra": "^1.0.0",
+    "fs-extra": "^2.1.2",
     "mkdirp": "^0.5.1",
     "node-localstorage": "^1.3.0",
     "request": "^2.78.0",
     "sauce-connect-launcher": "^1.0.0",
-    "selenium-webdriver": "3.0.1",
+    "selenium-webdriver": "3.4.0",
     "semver": "^5.3.0",
     "which": "^1.2.11",
     "yauzl": "^2.7.0"
   },
-  "optionalDependencies": {
-    "chromedriver": "^2.26.1",
-    "geckodriver": "^1.2.0",
-    "operadriver": "^1.0.0"
-  },
   "files": [
     "src/"
   ]
diff --git a/test/browser-usage.js b/test/browser-usage.js
index d053729..dc5865a 100644
--- a/test/browser-usage.js
+++ b/test/browser-usage.js
@@ -116,7 +116,7 @@ describe('Test Usage of Browsers', function() {
 
       it('should get null for raw version output if no executable found', function() {
         sinonStubs.push(
-          sinon.stub(localBrowser, 'getExecutablePath', () => {
+          sinon.stub(localBrowser, 'getExecutablePath').callsFake(() => {
             return null;
           })
         );
@@ -130,7 +130,7 @@ describe('Test Usage of Browsers', function() {
 
       it('should get -1 for version number if no executable found', function() {
         sinonStubs.push(
-          sinon.stub(localBrowser, 'getExecutablePath', () => {
+          sinon.stub(localBrowser, 'getExecutablePath').callsFake(() => {
             return null;
           })
         );
@@ -144,7 +144,7 @@ describe('Test Usage of Browsers', function() {
 
       it('should get -1 for an unexpected raw version string', function() {
         sinonStubs.push(
-          sinon.stub(localBrowser, 'getRawVersionString', () => {
+          sinon.stub(localBrowser, 'getRawVersionString').callsFake(() => {
             return 'ImTotallyMadeUp 12345678.asdf.12345678.asdf';
           })
         );
diff --git a/test/expiration-behavior.js b/test/expiration-behavior.js
index 727005d..56a71f2 100644
--- a/test/expiration-behavior.js
+++ b/test/expiration-behavior.js
@@ -104,19 +104,20 @@ describe('Test Download Manager - Browser Expiration', function() {
   before(function() {
     seleniumAssistant.setBrowserInstallDir(testPath);
 
-    const dlChromeStub = sinon.stub(downloadManager, '_downlaodChrome',
-      (release, installDir) => {
+    const dlChromeStub = sinon.stub(downloadManager, '_downlaodChrome')
+      .callsFake((release, installDir) => {
         browserDownloads.chrome[release] = true;
         return Promise.resolve();
       });
 
-    const dlFFStub = sinon.stub(downloadManager, '_downloadFirefox',
-      (release, installDir) => {
+    const dlFFStub = sinon.stub(downloadManager, '_downloadFirefox')
+      .callsFake((release, installDir) => {
         browserDownloads.firefox[release] = true;
         return Promise.resolve();
       });
 
-    const isValidStub = sinon.stub(LocalBrowser.prototype, 'isValid', () => {
+    const isValidStub = sinon.stub(LocalBrowser.prototype, 'isValid')
+    .callsFake(() => {
       return true;
     });
 
diff --git a/test/local-browser.js b/test/local-browser.js
index 70bdee5..51f7c9c 100644
--- a/test/local-browser.js
+++ b/test/local-browser.js
@@ -45,7 +45,8 @@ describe('LocalBrowser', function() {
 
     // getPrettyReleaseNames needs to be stubbed since we are instantiating
     // LocalBrowser directly rather than extending it.
-    const stub = sinon.stub(LocalBrowser, 'getPrettyReleaseNames', () => {
+    const stub = sinon.stub(LocalBrowser, 'getPrettyReleaseNames')
+    .callsFake(() => {
       return releaseNames;
     });
     sinonStubs.push(stub);
@@ -253,7 +254,8 @@ describe('LocalBrowser', function() {
       'exampledriver': null,
     });
 
-    const stub = sinon.stub(ProxiedLocalBrowser, 'getPrettyReleaseNames', () => {
+    const stub = sinon.stub(ProxiedLocalBrowser, 'getPrettyReleaseNames')
+    .callsFake(() => {
       return releaseNames;
     });
     sinonStubs.push(stub);
@@ -281,7 +283,8 @@ describe('LocalBrowser', function() {
       },
     });
 
-    const stub = sinon.stub(ProxiedLocalBrowser, 'getPrettyReleaseNames', () => {
+    const stub = sinon.stub(ProxiedLocalBrowser, 'getPrettyReleaseNames')
+    .callsFake(() => {
       return releaseNames;
     });
     sinonStubs.push(stub);
diff --git a/test/selenium-assistant.js b/test/selenium-assistant.js
index 3e25475..0b2696d 100644
--- a/test/selenium-assistant.js
+++ b/test/selenium-assistant.js
@@ -103,7 +103,7 @@ describe('SeleniumAssistant', function() {
     this.timeout(NUM_OF_BROWSERS * 3000 * 1000);
 
     let consoleCalls = 0;
-    const stub = sinon.stub(console, 'log', (input) => {
+    const stub = sinon.stub(console, 'log').callsFake((input) => {
       consoleCalls++;
     });
     sinonStubs.push(stub);
@@ -121,7 +121,7 @@ describe('SeleniumAssistant', function() {
     this.timeout(NUM_OF_BROWSERS * 3000 * 1000);
 
     let consoleCalls = 0;
-    const stub = sinon.stub(console, 'log', () => {
+    const stub = sinon.stub(console, 'log').callsFake(() => {
       consoleCalls++;
     });
     sinonStubs.push(stub);