diff --git a/lib/commands/actions.js b/lib/commands/actions.js
index 2a20f84b..a521dd38 100644
--- a/lib/commands/actions.js
+++ b/lib/commands/actions.js
@@ -1,9 +1,9 @@
 import androidHelpers from '../android-helpers';
-import { fs, util, tempDir, imageUtil } from '@appium/support';
+import {fs, util, tempDir, imageUtil} from '@appium/support';
 import path from 'path';
 import B from 'bluebird';
-import { exec } from 'teen_process';
-import { requireArgs } from '../utils';
+import {exec} from 'teen_process';
+import {requireArgs} from '../utils';
 
 const swipeStepsPerSec = 28;
 const dragStepsPerSec = 40;
@@ -12,21 +12,21 @@ const commands = {};
 const helpers = {};
 const extensions = {};
 
-commands.keyevent = async function keyevent (keycode, metastate = null) {
+commands.keyevent = async function keyevent(keycode, metastate = null) {
   // TODO deprecate keyevent; currently wd only implements keyevent
   this.log.warn('keyevent will be deprecated use pressKeyCode');
   return await this.pressKeyCode(keycode, metastate);
 };
 
-commands.pressKeyCode = async function pressKeyCode (keycode, metastate = null) {
+commands.pressKeyCode = async function pressKeyCode(keycode, metastate = null) {
   return await this.bootstrap.sendAction('pressKeyCode', {keycode, metastate});
 };
 
-commands.longPressKeyCode = async function longPressKeyCode (keycode, metastate = null) {
+commands.longPressKeyCode = async function longPressKeyCode(keycode, metastate = null) {
   return await this.bootstrap.sendAction('longPressKeyCode', {keycode, metastate});
 };
 
-commands.getOrientation = async function getOrientation () {
+commands.getOrientation = async function getOrientation() {
   let params = {
     naturalOrientation: !!this.opts.androidNaturalOrientation,
   };
@@ -34,7 +34,7 @@ commands.getOrientation = async function getOrientation () {
   return orientation.toUpperCase();
 };
 
-commands.setOrientation = async function setOrientation (orientation) {
+commands.setOrientation = async function setOrientation(orientation) {
   orientation = orientation.toUpperCase();
   let params = {
     orientation,
@@ -43,24 +43,23 @@ commands.setOrientation = async function setOrientation (orientation) {
   return await this.bootstrap.sendAction('orientation', params);
 };
 
-commands.fakeFlick = async function fakeFlick (xSpeed, ySpeed) {
+commands.fakeFlick = async function fakeFlick(xSpeed, ySpeed) {
   return await this.bootstrap.sendAction('flick', {xSpeed, ySpeed});
 };
 
-commands.fakeFlickElement = async function fakeFlickElement (elementId, xoffset, yoffset, speed) {
+commands.fakeFlickElement = async function fakeFlickElement(elementId, xoffset, yoffset, speed) {
   let params = {xoffset, yoffset, speed, elementId};
   return await this.bootstrap.sendAction('element:flick', params);
 };
 
-commands.swipe = async function swipe (startX, startY, endX, endY, duration, touchCount, elId) {
+commands.swipe = async function swipe(startX, startY, endX, endY, duration, touchCount, elId) {
   if (startX === 'null') {
     startX = 0.5;
   }
   if (startY === 'null') {
     startY = 0.5;
   }
-  let swipeOpts = {startX, startY, endX, endY,
-                   steps: Math.round(duration * swipeStepsPerSec)};
+  let swipeOpts = {startX, startY, endX, endY, steps: Math.round(duration * swipeStepsPerSec)};
   // going the long way and checking for undefined and null since
   // we can't be assured `elId` is a string and not an int
   if (util.hasValue(elId)) {
@@ -69,7 +68,7 @@ commands.swipe = async function swipe (startX, startY, endX, endY, duration, tou
   return await this.doSwipe(swipeOpts);
 };
 
-commands.doSwipe = async function doSwipe (swipeOpts) {
+commands.doSwipe = async function doSwipe(swipeOpts) {
   if (util.hasValue(swipeOpts.elementId)) {
     return await this.bootstrap.sendAction('element:swipe', swipeOpts);
   } else {
@@ -77,22 +76,40 @@ commands.doSwipe = async function doSwipe (swipeOpts) {
   }
 };
 
-commands.pinchClose = async function pinchClose (startX, startY, endX, endY, duration, percent, steps, elId) {
+commands.pinchClose = async function pinchClose(
+  startX,
+  startY,
+  endX,
+  endY,
+  duration,
+  percent,
+  steps,
+  elId
+) {
   let pinchOpts = {
     direction: 'in',
     elementId: elId,
     percent,
-    steps
+    steps,
   };
   return await this.bootstrap.sendAction('element:pinch', pinchOpts);
 };
 
-commands.pinchOpen = async function pinchOpen (startX, startY, endX, endY, duration, percent, steps, elId) {
+commands.pinchOpen = async function pinchOpen(
+  startX,
+  startY,
+  endX,
+  endY,
+  duration,
+  percent,
+  steps,
+  elId
+) {
   let pinchOpts = {direction: 'out', elementId: elId, percent, steps};
   return await this.bootstrap.sendAction('element:pinch', pinchOpts);
 };
 
-commands.flick = async function flick (element, xSpeed, ySpeed, xOffset, yOffset, speed) {
+commands.flick = async function flick(element, xSpeed, ySpeed, xOffset, yOffset, speed) {
   if (element) {
     await this.fakeFlickElement(element, xOffset, yOffset, speed);
   } else {
@@ -100,16 +117,29 @@ commands.flick = async function flick (element, xSpeed, ySpeed, xOffset, yOffset
   }
 };
 
-commands.drag = async function drag (startX, startY, endX, endY, duration, touchCount, elementId, destElId) {
+commands.drag = async function drag(
+  startX,
+  startY,
+  endX,
+  endY,
+  duration,
+  touchCount,
+  elementId,
+  destElId
+) {
   let dragOpts = {
-    elementId, destElId, startX, startY, endX, endY,
-    steps: Math.round(duration * dragStepsPerSec)
+    elementId,
+    destElId,
+    startX,
+    startY,
+    endX,
+    endY,
+    steps: Math.round(duration * dragStepsPerSec),
   };
   return await this.doDrag(dragOpts);
-
 };
 
-commands.doDrag = async function doDrag (dragOpts) {
+commands.doDrag = async function doDrag(dragOpts) {
   if (util.hasValue(dragOpts.elementId)) {
     return await this.bootstrap.sendAction('element:drag', dragOpts);
   } else {
@@ -117,7 +147,25 @@ commands.doDrag = async function doDrag (dragOpts) {
   }
 };
 
-commands.lock = async function lock (seconds) {
+/**
+ * @typedef {Object} LockOptions
+ * @property {number?} seconds The number to keep the locked.
+ * 0 or empty value will keep the device locked.
+ */
+
+/**
+ * Lock the device (and optionally unlock it after a certain amount of time).
+
+ * @param {LockOptions} opts
+ * @throws {Error} if lock or unlock operation fails
+ */
+
+commands.mobileLock = async function mobileLock(opts = {}) {
+  const {seconds} = opts;
+  return await this.lock(seconds);
+};
+
+commands.lock = async function lock(seconds) {
   await this.adb.lock();
   if (isNaN(seconds)) {
     return;
@@ -131,23 +179,23 @@ commands.lock = async function lock (seconds) {
   await this.unlock();
 };
 
-commands.isLocked = async function isLocked () {
+commands.isLocked = async function isLocked() {
   return await this.adb.isScreenLocked();
 };
 
-commands.unlock = async function unlock () {
+commands.unlock = async function unlock() {
   return await androidHelpers.unlock(this, this.adb, this.caps);
 };
 
-commands.openNotifications = async function openNotifications () {
+commands.openNotifications = async function openNotifications() {
   return await this.bootstrap.sendAction('openNotification');
 };
 
-commands.setLocation = async function setLocation (latitude, longitude) {
+commands.setLocation = async function setLocation(latitude, longitude) {
   return await this.adb.sendTelnetCommand(`geo fix ${longitude} ${latitude}`);
 };
 
-commands.fingerprint = async function fingerprint (fingerprintId) {
+commands.fingerprint = async function fingerprint(fingerprintId) {
   if (!this.isEmulator()) {
     this.log.errorAndThrow('fingerprint method is only available for emulators');
   }
@@ -174,7 +222,7 @@ commands.mobileFingerprint = async function mobileFingerprint(opts = {}) {
   await this.fingerprint(fingerprintId);
 };
 
-commands.sendSMS = async function sendSMS (phoneNumber, message) {
+commands.sendSMS = async function sendSMS(phoneNumber, message) {
   if (!this.isEmulator()) {
     this.log.errorAndThrow('sendSMS method is only available for emulators');
   }
@@ -198,7 +246,7 @@ commands.mobileSendSms = async function mobileSendSms(opts = {}) {
   await this.sendSMS(phoneNumber, message);
 };
 
-commands.gsmCall = async function gsmCall (phoneNumber, action) {
+commands.gsmCall = async function gsmCall(phoneNumber, action) {
   if (!this.isEmulator()) {
     this.log.errorAndThrow('gsmCall method is only available for emulators');
   }
@@ -222,7 +270,7 @@ commands.mobileGsmCall = async function mobileGsmCall(opts = {}) {
   await this.gsmCall(phoneNumber, action);
 };
 
-commands.gsmSignal = async function gsmSignal (signalStrengh) {
+commands.gsmSignal = async function gsmSignal(signalStrengh) {
   if (!this.isEmulator()) {
     this.log.errorAndThrow('gsmSignal method is only available for emulators');
   }
@@ -245,7 +293,7 @@ commands.mobileGsmSignal = async function mobileGsmSignal(opts = {}) {
   await this.gsmSignal(strength);
 };
 
-commands.gsmVoice = async function gsmVoice (state) {
+commands.gsmVoice = async function gsmVoice(state) {
   if (!this.isEmulator()) {
     this.log.errorAndThrow('gsmVoice method is only available for emulators');
   }
@@ -268,7 +316,7 @@ commands.mobileGsmVoice = async function mobileGsmVoice(opts = {}) {
   await this.gsmVoice(state);
 };
 
-commands.powerAC = async function powerAC (state) {
+commands.powerAC = async function powerAC(state) {
   if (!this.isEmulator()) {
     this.log.errorAndThrow('powerAC method is only available for emulators');
   }
@@ -291,7 +339,7 @@ commands.mobilePowerAc = async function mobilePowerAc(opts = {}) {
   await this.powerAC(state);
 };
 
-commands.powerCapacity = async function powerCapacity (batteryPercent) {
+commands.powerCapacity = async function powerCapacity(batteryPercent) {
   if (!this.isEmulator()) {
     this.log.errorAndThrow('powerCapacity method is only available for emulators');
   }
@@ -314,7 +362,7 @@ commands.mobilePowerCapacity = async function mobilePowerCapacity(opts = {}) {
   await this.powerCapacity(percent);
 };
 
-commands.networkSpeed = async function networkSpeed (networkSpeed) {
+commands.networkSpeed = async function networkSpeed(networkSpeed) {
   if (!this.isEmulator()) {
     this.log.errorAndThrow('networkSpeed method is only available for emulators');
   }
@@ -349,7 +397,7 @@ commands.mobileNetworkSpeed = async function mobileNetworkSpeed(opts = {}) {
  * @throws {Error} - If value for the se sor is not defined
  * @throws {Error} - If deviceType is not an emulator
  */
-commands.sensorSet = async function sensorSet (sensor = {}) {
+commands.sensorSet = async function sensorSet(sensor = {}) {
   const {sensorType, value} = sensor;
   if (!util.hasValue(sensorType)) {
     this.log.errorAndThrow(`'sensorType' argument is required`);
@@ -368,7 +416,7 @@ commands.sensorSet = async function sensorSet (sensor = {}) {
  * @param {Object} opts
  * @returns {Promise<Buffer>}
  */
-helpers.getScreenshotDataWithAdbShell = async function getScreenshotDataWithAdbShell (adb, opts) {
+helpers.getScreenshotDataWithAdbShell = async function getScreenshotDataWithAdbShell(adb, opts) {
   const localFile = await tempDir.path({prefix: 'appium', suffix: '.png'});
   if (await fs.exists(localFile)) {
     await fs.unlink(localFile);
@@ -377,7 +425,7 @@ helpers.getScreenshotDataWithAdbShell = async function getScreenshotDataWithAdbS
     const pngDir = opts.androidScreenshotPath || '/data/local/tmp/';
     const png = path.posix.resolve(pngDir, 'screenshot.png');
     await adb.shell(['/system/bin/rm', `${png};`, '/system/bin/screencap', '-p', png]);
-    if (!await adb.fileSize(png)) {
+    if (!(await adb.fileSize(png))) {
       throw new Error('The size of the taken screenshot equals to zero.');
     }
     await adb.pull(png, localFile);
@@ -393,7 +441,7 @@ helpers.getScreenshotDataWithAdbShell = async function getScreenshotDataWithAdbS
  * @param {ADB} adb
  * @returns {Promise<Buffer>}
  */
-helpers.getScreenshotDataWithAdbExecOut = async function getScreenshotDataWithAdbExecOut (adb) {
+helpers.getScreenshotDataWithAdbExecOut = async function getScreenshotDataWithAdbExecOut(adb) {
   const {stdout, stderr, code} = await exec(
     adb.executable.path,
     [...adb.executable.defaultArgs, 'exec-out', '/system/bin/screencap', '-p'],
@@ -411,7 +459,7 @@ helpers.getScreenshotDataWithAdbExecOut = async function getScreenshotDataWithAd
   return stdout;
 };
 
-commands.getScreenshot = async function getScreenshot () {
+commands.getScreenshot = async function getScreenshot() {
   const apiLevel = await this.adb.getApiLevel();
   let image = null;
   if (apiLevel > 20) {
@@ -420,15 +468,18 @@ commands.getScreenshot = async function getScreenshot () {
       // to be executed. Unfortunately, exec-out option is only supported by newer Android/SDK versions (5.0 and later)
       image = await this.getScreenshotDataWithAdbExecOut(this.adb);
     } catch (e) {
-      this.log.info(`Cannot get screenshot data with 'adb exec-out' because of '${e.message}'. ` +
-        `Defaulting to 'adb shell' call`);
+      this.log.info(
+        `Cannot get screenshot data with 'adb exec-out' because of '${e.message}'. ` +
+          `Defaulting to 'adb shell' call`
+      );
     }
   }
   if (!image) {
     try {
       image = await this.getScreenshotDataWithAdbShell(this.adb, this.opts);
     } catch (e) {
-      const err = `Cannot get screenshot data because of '${e.message}'. ` +
+      const err =
+        `Cannot get screenshot data because of '${e.message}'. ` +
         `Make sure the 'LayoutParams.FLAG_SECURE' is not set for ` +
         `the current view`;
       this.log.errorAndThrow(err);
@@ -438,7 +489,10 @@ commands.getScreenshot = async function getScreenshot () {
     // Android bug 8433742 - rotate screenshot if screen is rotated
     let screenOrientation = await this.adb.getScreenOrientation();
     try {
-      image = await imageUtil.requireSharp()(image).rotate(-90 * screenOrientation).toBuffer();
+      image = await imageUtil
+        .requireSharp()(image)
+        .rotate(-90 * screenOrientation)
+        .toBuffer();
     } catch (err) {
       this.log.warn(`Could not rotate screenshot due to error: ${err}`);
     }
@@ -447,5 +501,5 @@ commands.getScreenshot = async function getScreenshot () {
 };
 
 Object.assign(extensions, commands, helpers);
-export { commands, helpers };
+export {commands, helpers};
 export default extensions;
diff --git a/lib/commands/execute.js b/lib/commands/execute.js
index 730cfe88..b7171330 100644
--- a/lib/commands/execute.js
+++ b/lib/commands/execute.js
@@ -1,9 +1,9 @@
 import _ from 'lodash';
-import { errors, PROTOCOLS } from 'appium/driver';
+import {errors, PROTOCOLS} from 'appium/driver';
 
 const extensions = {};
 
-extensions.execute = async function execute (script, args) {
+extensions.execute = async function execute(script, args) {
   if (script.match(/^mobile:/)) {
     this.log.info(`Executing native command '${script}'`);
     script = script.replace(/^mobile:/, '').trim();
@@ -12,16 +12,17 @@ extensions.execute = async function execute (script, args) {
   if (!this.isWebContext()) {
     throw new errors.NotImplementedError();
   }
-  const endpoint = this.chromedriver.jwproxy.downstreamProtocol === PROTOCOLS.MJSONWP
-    ? '/execute'
-    : '/execute/sync';
+  const endpoint =
+    this.chromedriver.jwproxy.downstreamProtocol === PROTOCOLS.MJSONWP
+      ? '/execute'
+      : '/execute/sync';
   return await this.chromedriver.jwproxy.command(endpoint, 'POST', {
     script,
     args,
   });
 };
 
-extensions.executeMobile = async function executeMobile (mobileCommand, opts = {}) {
+extensions.executeMobile = async function executeMobile(mobileCommand, opts = {}) {
   const mobileCommandsMapping = {
     shell: 'mobileShell',
 
@@ -66,6 +67,7 @@ extensions.executeMobile = async function executeMobile (mobileCommand, opts = {
 
     getContexts: 'mobileGetContexts',
 
+    lock: 'mobileLock',
     unlock: 'mobileUnlock',
 
     refreshGpsCache: 'mobileRefreshGpsCache',
@@ -82,8 +84,10 @@ extensions.executeMobile = async function executeMobile (mobileCommand, opts = {
   };
 
   if (!_.has(mobileCommandsMapping, mobileCommand)) {
-    throw new errors.UnknownCommandError(`Unknown mobile command "${mobileCommand}". ` +
-      `Only ${_.keys(mobileCommandsMapping)} commands are supported.`);
+    throw new errors.UnknownCommandError(
+      `Unknown mobile command "${mobileCommand}". ` +
+        `Only ${_.keys(mobileCommandsMapping)} commands are supported.`
+    );
   }
   return await this[mobileCommandsMapping[mobileCommand]](opts);
 };