diff --git a/lib/main.js b/lib/main.js
index 7e5bc6e8..ff47593f 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -8,7 +8,6 @@ const execFile = require('child_process').execFile
 const fs = require('fs-extra')
 const packageJson = require(path.join(__dirname, '..', 'package.json'))
 const minimatch = require('minimatch')
-const async = require('async')
 const zip = new (require('node-zip'))()
 const dotenv = require('dotenv')
 const ScheduleEvents = require(path.join(__dirname, 'schedule_events'))
@@ -765,127 +764,117 @@ Lambda.prototype.package = function (program) {
   })
 }
 
-Lambda.prototype.deploy = function (program) {
-  var _this = this
-  var regions = program.region.split(',')
-  _this._archive(program, function (err, buffer) {
-    if (err) {
-      throw err
-    }
-
-    console.log('=> Reading zip file to memory')
-    var params = _this._params(program, buffer)
-
-    console.log('=> Reading event source file to memory')
-    var eventSourceList = _this._eventSourceList(program)
+Lambda.prototype._deployToRegion = function (program, params, region) {
+  const _this = this
+  console.log('=> Reading event source file to memory')
+  const eventSourceList = _this._eventSourceList(program)
 
-    async.map(regions, function (region, cb) {
-      console.log('=> Uploading zip file to AWS Lambda ' + region + ' with parameters:')
-      console.log(params)
-
-      var awsSecurity = {
-        region: region
-      }
-
-      if (program.profile) {
-        aws.config.credentials = new aws.SharedIniFileCredentials({
-          profile: program.profile
-        })
-      } else {
-        awsSecurity.accessKeyId = program.accessKey
-        awsSecurity.secretAccessKey = program.secretKey
-      }
+  return new Promise((resolve, reject) => {
+    console.log('=> Uploading zip file to AWS Lambda ' + region + ' with parameters:')
+    console.log(params)
 
-      if (program.sessionToken) {
-        awsSecurity.sessionToken = program.sessionToken
-      }
+    const awsSecurity = { region: region }
 
-      if (program.deployTimeout) {
-        aws.config.httpOptions.timeout = parseInt(program.deployTimeout)
-      }
+    if (program.profile) {
+      aws.config.credentials = new aws.SharedIniFileCredentials({
+        profile: program.profile
+      })
+    } else {
+      awsSecurity.accessKeyId = program.accessKey
+      awsSecurity.secretAccessKey = program.secretKey
+    }
 
-      aws.config.update(awsSecurity)
+    if (program.sessionToken) {
+      awsSecurity.sessionToken = program.sessionToken
+    }
 
-      var lambda = new aws.Lambda({
-        apiVersion: '2015-03-31'
-      })
-      var scheduleEvents = new ScheduleEvents(aws)
+    if (program.deployTimeout) {
+      aws.config.httpOptions.timeout = parseInt(program.deployTimeout)
+    }
 
-      // Checking function
-      return lambda.getFunction({
-        'FunctionName': params.FunctionName
-      }, (err) => {
-        if (err) {
-          // Function does not exist
-          return _this._uploadNew(lambda, params).then((results) => {
-            console.log('=> Zip file(s) done uploading. Results follow: ')
-            console.log(results)
+    aws.config.update(awsSecurity)
 
-            // This code is on its way to Promise.
-            // From now on, callback will not be used.
-            return Promise.all([
-              _this._updateEventSources(
-                lambda,
-                params.FunctionName,
-                [],
-                eventSourceList.EventSourceMappings
-              ),
-              _this._updateScheduleEvents(
-                scheduleEvents,
-                results.FunctionArn,
-                eventSourceList.ScheduleEvents
-              )
-            ]).then((results) => {
-              cb(null, results)
-            }).catch((err) => {
-              cb(err)
-            })
-          }).catch((err) => {
-            return Promise.reject(err)
-          })
-        }
+    const lambda = new aws.Lambda({ apiVersion: '2015-03-31' })
+    const scheduleEvents = new ScheduleEvents(aws)
 
-        // Function exists
-        _this._listEventSourceMappings(lambda, {
-          'FunctionName': params.FunctionName
-        }, (err, existingEventSourceList) => {
-          if (err) {
-            throw err
-          }
+    // Checking function
+    return lambda.getFunction({
+      'FunctionName': params.FunctionName
+    }, (err) => {
+      if (err) {
+        // Function does not exist
+        return _this._uploadNew(lambda, params).then((results) => {
+          console.log('=> Zip file(s) done uploading. Results follow: ')
+          console.log(results)
 
-          // This code is on its way to Promise.
-          // From now on, callback will not be used.
           return Promise.all([
-            _this._uploadExisting(lambda, params).then((results) => {
-              console.log('=> Zip file(s) done uploading. Results follow: ')
-              console.log(results)
-              return _this._updateScheduleEvents(
-                scheduleEvents,
-                results.FunctionArn,
-                eventSourceList.ScheduleEvents
-              )
-            }).catch((err) => {
-              return Promise.reject(err)
-            }),
             _this._updateEventSources(
               lambda,
               params.FunctionName,
-              existingEventSourceList,
+              [],
               eventSourceList.EventSourceMappings
+            ),
+            _this._updateScheduleEvents(
+              scheduleEvents,
+              results.FunctionArn,
+              eventSourceList.ScheduleEvents
             )
           ]).then((results) => {
-            cb(null, results)
+            resolve(results)
           }).catch((err) => {
-            cb(err)
+            reject(err)
           })
+        }).catch((err) => {
+          reject(err)
         })
-      })
-    }, function (err, results) {
-      if (err) {
-        throw err
       }
-      const resultsIsEmpty = results.filter(function (result) {
-        return result.filter(function (res) {
+
+      // Function exists
+      _this._listEventSourceMappings(lambda, {
+        'FunctionName': params.FunctionName
+      }, (err, existingEventSourceList) => {
+        if (err) return reject(err)
+
+        return Promise.all([
+          _this._uploadExisting(lambda, params).then((results) => {
+            console.log('=> Zip file(s) done uploading. Results follow: ')
+            console.log(results)
+            return _this._updateScheduleEvents(
+              scheduleEvents,
+              results.FunctionArn,
+              eventSourceList.ScheduleEvents
+            )
+          }),
+          _this._updateEventSources(
+            lambda,
+            params.FunctionName,
+            existingEventSourceList,
+            eventSourceList.EventSourceMappings
+          )
+        ]).then((results) => {
+          resolve(results)
+        }).catch((err) => {
+          reject(err)
+        })
+      })
+    })
+  })
+}
+
+Lambda.prototype.deploy = function (program) {
+  const _this = this
+  const regions = program.region.split(',')
+  _this._archive(program, (err, buffer) => {
+    if (err) throw err
+
+    console.log('=> Reading zip file to memory')
+    const params = _this._params(program, buffer)
+
+    Promise.all(regions.map((region) => {
+      return _this._deployToRegion(program, params, region)
+    })).then((results) => {
+      const resultsIsEmpty = results.filter((result) => {
+        return result.filter((res) => {
           return res.length > 0
         }).length > 0
       }).length === 0
@@ -893,6 +882,8 @@ Lambda.prototype.deploy = function (program) {
         console.log('=> All tasks done. Results follow: ')
         console.log(JSON.stringify(results, null, ' '))
       }
+    }).catch((err) => {
+      console.log(err)
     })
   })
 }
diff --git a/test/main.js b/test/main.js
index a6700e7d..0f22cbb2 100644
--- a/test/main.js
+++ b/test/main.js
@@ -1022,7 +1022,11 @@ describe('lib/main', function () {
     })
   })
 
+  describe('Lambda.prototype._deployToRegion()', () => {
+    it('Since `aws-mock` does not correspond to `request.on`, it is impossible to test with Mock')
+  })
+
   describe('Lambda.prototype.deploy()', () => {
-    it('TODO: Add test. Since the current deploy function is hard to test, skip')
+    it('Since `aws-mock` does not correspond to `request.on`, it is impossible to test with Mock')
   })
 })