diff --git a/README.md b/README.md
index d351afb..d8f73b9 100644
--- a/README.md
+++ b/README.md
@@ -1,90 +1,128 @@
-Puppet Module for Android SDK
-=============================
+Puppet Module for Android SDK and NDK
+=====================================
 
 [![Build Status](https://maestro.maestrodev.com/api/v1/projects/58/compositions/443/badge/icon)](https://maestro.maestrodev.com/projects/58/compositions/443)
 
-This Puppet module is used to install the Android SDK and NDK, 
-along with platforms and other add-ons.
-You may need to install Java separately.
+This Puppet module is used to install the Android SDK and NDK, along with
+add-ons, build-tools, extras, platforms, and system images. You may need to
+install Java separately.
 
 Supported platforms:
 
 * Linux (RedHat, Debian families)
-* Mac OS X
+* OS X (requires `wget` to be installed)
 
 Examples
 --------
 
-To install the Android SDK in the default location (/usr/local/android on both Linux
-and Mac OS X) you simply include the android class like so.
+To install the Android SDK and platform tools in the default location
+(`/usr/local/android` on both Linux and OS X) you simply include the `android`
+class like so:
 
-    class { 'java': } ->
-    class { 'android': }
+```
+class { 'java': } ->
+class { 'android': }
+```
 
 You can also change the default parameters like so:
 
 ```
-  class { 'android':
-    user       => 'someuser',
-    group      => 'somegroup',
-    installdir => '/path/to/your/dir',
-  }
+class { 'android':
+  user       => 'someuser',
+  group      => 'somegroup',
+  installdir => '/path/to/your/dir',
+}
 ```
 
 You can install the Android NDK like so:
 
 ```
-class { 'android::ndk' :
+class { 'android::ndk':
   ndk_version => 'android-ndk-r10c-linux-x86_64.bin'
 }
 ```
 
-Note that the NDK is downloaded and executed, so only newer NDK versions are supported. The older tar archives will not work properly.
+Note that the Android NDK is downloaded and executed, so only newer NDK
+versions are supported. The older tar archives will not work properly.
 
-To install an android platform, do it like so:
+To install an Android Platform, do it like so:
 
 ```
-  android::platform { 'android-16': }
+android::platform { 'android-16': }
 ```
 
 You can also install add-ons:
 
 ```
-  android::addon { 'addon-google_apis-google-16': }
+android::addon { 'addon-google_apis-google-16': }
+```
+
+Or extras:
+
+```
+android::extra { 'extra-google-play_billing': }
 ```
 
-Or extra's:
+Or system images:
 
 ```
-  android::extra { 'extra-google-play_billing': }
+android::system_images { 'sys-img-armeabi-v7a-android-23': }
 ```
 
-To install Android SDK Build-tools, revision 19.0.1
+To install the Android SDK Build-tools, revision 19.0.1:
 
 ```
-  android::build_tools { 'build-tools-19.0.1': }
+android::build_tools { 'build-tools-19.0.1': }
 ```
 
-Tip: to get the appropriate name of the add-ons/extras run the following command:
+For add-ons, extras, platforms, and system images, the revision number can be
+specified using the optional `revision` parameter:
 
 ```
-/usr/local/android/android-sdk-macosx/tools/android list sdk -u --all --extended|grep " or "
+android::extra { 'extra-google-m2repository':
+  revision => '24',
+}
+```
+
+The add-on, extra, platform, or system image will only be upgraded only if the
+installed revision is not equal to the specified revision. For build-tools, the
+revision number forms part of the name of the build-tool, hence there is no
+`revision` parameter.
+
+The `revision` parameter can also take the value `present` that initially
+installs the latest version of the add-on, extra, platform, or system image, but
+does not upgrade it when a new version becomes available, and the value `latest`
+that always upgrades the add-on, extra, platform, or system image to the latest
+version:
+
+```
+android::extra { 'extra-android-m2repository':
+  revision => latest,
+}
+```
+
+Tip: To get the appropriate name of the add-on, extra, platform, or system
+image, run the following command:
+
+```
+android list sdk --all --extended --no-ui | grep " or "
 ```
 
 License
 -------
+
 ```
-  Copyright 2012-2014 MaestroDev
+Copyright 2012-2016 MaestroDev
 
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
 
-      http://www.apache.org/licenses/LICENSE-2.0
+    http://www.apache.org/licenses/LICENSE-2.0
 
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
 ```
diff --git a/manifests/addon.pp b/manifests/addon.pp
index 91fa2c4..a7c6bfb 100644
--- a/manifests/addon.pp
+++ b/manifests/addon.pp
@@ -2,6 +2,16 @@
 #
 # Installs an Android SDK add-on package.
 #
+# === Examples
+#
+# To install an add-on package:
+#   android::addon { 'addon-google_apis-google-16': }
+#
+# === Parameters
+#
+# [*revision*] The revision number of the specified add-on package or a value of
+#   'latest' or 'present'
+#
 # === Authors
 #
 # Etienne Pelletier <epelletier@maestrodev.com>
@@ -10,10 +20,12 @@
 #
 # Copyright 2012 MaestroDev, unless otherwise noted.
 #
-define android::addon() {
+define android::addon(
+  $revision = 'present',
+) {
 
-  android::package{ $title:
-    type => 'addon',
+  android::package { $title:
+    revision => $revision,
+    type     => 'addon',
   }
-
 }
diff --git a/manifests/build_tools.pp b/manifests/build_tools.pp
index 7e9e9ef..c7a94fa 100644
--- a/manifests/build_tools.pp
+++ b/manifests/build_tools.pp
@@ -1,6 +1,11 @@
-# == Class: android::build_tools
+# == Define: android::build_tools
 #
-# Installs the Android SDK build-tools.
+# Installs an Android SDK build-tools package.
+#
+# === Examples
+#
+# To install a build-tools package:
+#   android::build_tools { 'build-tools-19.0.1': }
 #
 # === Authors
 #
@@ -8,12 +13,11 @@
 #
 # === Copyright
 #
-# Copyright 2013 Philip Schiffer
+# Copyright 2013 Philip Schiffer.
 #
 define android::build_tools() {
 
-  android::package{ $title:
+  android::package { $title:
     type => 'build-tools',
   }
-
 }
diff --git a/manifests/extra.pp b/manifests/extra.pp
index 8c5e605..cd5d1b2 100644
--- a/manifests/extra.pp
+++ b/manifests/extra.pp
@@ -1,6 +1,16 @@
 # == Define: android::extra
 #
-# Installs an Android SDK "extra's" package.
+# Installs an Android SDK extra package.
+#
+# === Examples
+#
+# To install an extra package:
+#   android::extra { 'extra-google-play_billing': }
+#
+# === Parameters
+#
+# [*revision*] The revision number of the specified extra package or a value of
+#   'latest' or 'present'
 #
 # === Authors
 #
@@ -10,10 +20,12 @@
 #
 # Copyright 2012 MaestroDev, unless otherwise noted.
 #
-define android::extra() {
+define android::extra(
+  $revision = 'present',
+) {
 
-  android::package{ $title:
-    type => 'extra',
+  android::package { $title:
+    revision => $revision,
+    type     => 'extra',
   }
-
 }
diff --git a/manifests/init.pp b/manifests/init.pp
index c3b21bc..bfabe63 100644
--- a/manifests/init.pp
+++ b/manifests/init.pp
@@ -1,15 +1,25 @@
 # == Class: android
 #
-# This class is used to install the android SDK and platform tools
+# This class is used to install the Android SDK and platform tools.
 #
-# === Parameters:
+# === Examples
 #
-# [*version*] the SDK version
-# [*user*] used to set the file ownership of the installed SDK
-# [*group*] used to set the file ownership of the installed SDK
-# [*installdir*] the install directory.
-# [*proxy_host*] the proxy server host name (used by the android tool)
-# [*proxy_port*] the proxy server port (used by the android tool)
+# To install the Android SDK:
+#   class { 'java': } ->
+#   class { 'android':
+#     user       => 'someuser',
+#     group      => 'somegroup',
+#     installdir => '/path/to/your/dir',
+#   }
+#
+# === Parameters
+#
+# [*version*] The SDK version
+# [*user*] Used to set the file ownership of the installed SDK
+# [*group*] Used to set the file ownership of the installed SDK
+# [*installdir*] The install directory
+# [*proxy_host*] The proxy server host name (used by the 'android' tool)
+# [*proxy_port*] The proxy server port (used by the 'android' tool)
 #
 # === Authors
 #
@@ -25,7 +35,21 @@
   $group      = $android::params::group,
   $installdir = $android::params::installdir,
   $proxy_host = $android::params::proxy_host,
-  $proxy_port = $android::params::proxy_port) inherits android::params {
+  $proxy_port = $android::params::proxy_port,
+) inherits android::params {
+
+  validate_re($version, '^\d+(?:\.\d+)*$', "Invalid version: ${version}")
+  validate_string($user)
+  validate_string($group)
+  validate_absolute_path($installdir)
+
+  if ($proxy_host != undef) {
+    validate_string($proxy_host, '^\d+$')
+  }
+
+  if ($proxy_port != undef) {
+    validate_re($proxy_port, '^\d+$', "Invalid proxy port: ${proxy_port}")
+  }
 
   anchor { 'android::begin': } ->
   class { 'android::paths': } ->
diff --git a/manifests/ndk.pp b/manifests/ndk.pp
index 1f85e60..09fd843 100644
--- a/manifests/ndk.pp
+++ b/manifests/ndk.pp
@@ -1,10 +1,21 @@
 # == Class: android::ndk
 #
 # This downloads and unpacks the Android NDK from Google's download
-# sever, or another specified server.
+# server, or another specified server.
 #
-# Note that the NDK is expected to be a self extracting, so the
-# older .tar.gz packages that are simply extracted will not be supported.
+# Note that the NDK is expected to be a self extracting, so the older '.tar.gz'
+# packages that are simply extracted will not be supported.
+#
+# === Examples
+#
+# To install the Android NDK r10c-linux-x86_64:
+#   class { 'android::ndk':
+#     ndk_version => 'android-ndk-r10c-linux-x86_64.bin'
+#   }
+#
+# === Parameters
+#
+# [*ndk_version*] The NDK version and architecture to install
 #
 # === Authors
 #
@@ -15,20 +26,28 @@
 # Copyright 2015 Sam Kerr, unless otherwise noted.
 #
 class android::ndk(
-  $ndk_version = $android::params::ndk_version
-)
-{
+  $ndk_version = $android::params::ndk_version,
+) {
+
+  validate_re($ndk_version, '\.bin$')
+
+  include android::paths
   include android::params
   include wget
 
+  if ( $::id == 'root' ) {
+    Exec { user => $android::user }
+  }
+
   $base_path = "http://dl.google.com/android/ndk/${ndk_version}"
   $ndk_installer = "${android::paths::installdir}/${ndk_version}"
+
   wget::fetch { 'download-androidndk':
     source      => $base_path,
     destination => $ndk_installer,
   } ->
   file { 'android-ndkexecutable':
-    ensure => present,
+    ensure => file,
     path   => $ndk_installer,
     owner  => $android::user,
     group  => $android::group,
@@ -36,7 +55,7 @@
   } ->
   exec { 'run-androidndk':
     command => "${ndk_installer} -y",
+    creates => regsubst($ndk_installer, '^(.*)\.bin$','\1'),
     cwd     => $android::params::installdir,
   }
-
 }
diff --git a/manifests/package.pp b/manifests/package.pp
index 35f24cd..13388ca 100644
--- a/manifests/package.pp
+++ b/manifests/package.pp
@@ -1,11 +1,27 @@
 # == Define: android::package
 #
-# This defined resource is used to install Android SDK packages
+# This defined resource is used to install Android SDK packages.
+#
+# === Examples
+#
+# To install the latest revision of a package:
+#   android::package { 'extra-android-m2repository':
+#     type     => 'extra',
+#     revision => 'latest',
+#   }
+#
+# To install a specified revision of a package:
+#   android::package { 'extra-android-m2repository':
+#     type     => 'extra',
+#     revision => '24',
+#   }
 #
 # === Parameters
 #
-# [*type*] One of platform-tools, platform, addon, extra or build-tools. Indicates
-# the type of package to install.
+# [*type*] The type of package to install. This must be 'addon', 'build-tools',
+#   'extra', 'platform', 'platform-tools', or 'system-images'.
+# [*revision*] The revision number of the specified package or a value of
+#   'latest' or 'present'
 #
 # === Authors
 #
@@ -15,7 +31,11 @@
 #
 # Copyright 2012 MaestroDev, unless otherwise noted.
 #
-define android::package($type) {
+define android::package(
+  $type,
+  $revision = 'present',
+) {
+
   include android
 
   if ( $::id == 'root' ) {
@@ -27,31 +47,52 @@
 
   case $type {
     'platform-tools': {
-      $creates = "${android::paths::sdk_home}/platform-tools"
+      $path = "${android::paths::sdk_home}/platform-tools"
     }
     'platform': {
-      $creates = "${android::paths::sdk_home}/platforms/${title}"
+      $path = "${android::paths::sdk_home}/platforms/${title}"
     }
     'system-images': {
       $title_parts = split($title, '-')
-      $creates = "${android::paths::sdk_home}/system-images/android-${title_parts[-1]}/default/${title_parts[2]}-${title_parts[3]}"
+      $path = "${android::paths::sdk_home}/system-images/android-${title_parts[-1]}/default/${title_parts[2]}-${title_parts[3]}"
     }
     'addon': {
-      $creates = "${android::paths::sdk_home}/add-ons/${title}"
+      $path = "${android::paths::sdk_home}/add-ons/${title}"
     }
     'extra': {
       $title_parts = split($title, '-')
-      $creates = "${android::paths::sdk_home}/extras/${title_parts[1]}/${title_parts[2]}"
+      $path = "${android::paths::sdk_home}/extras/${title_parts[1]}/${title_parts[2]}"
     }
     'build-tools': {
       $title_parts = split($title, '-')
-      $creates = "${android::paths::sdk_home}/build-tools/${title_parts[2]}"
+      $path = "${android::paths::sdk_home}/build-tools/${title_parts[2]}"
     }
     default: {
       fail("Unsupported package type: ${type}")
     }
   }
 
+  case $revision {
+    'latest': {
+      $creates = undef
+      $onlyif = "${android::paths::sdk_home}/tools/android list sdk --extended --no-ui ${proxy_host} ${proxy_port} | grep ${title}"
+      $unless = undef
+    }
+    'present': {
+      $creates = $path
+      $onlyif = undef
+      $unless = undef
+    }
+    /^\d+(?:\.\d+)*$/: {
+      $creates = undef
+      $onlyif = undef
+      $unless = "grep 'Pkg.Revision=${revision}' ${path}/source.properties"
+    }
+    default: {
+      fail("Invalid package revision: ${revision}")
+    }
+  }
+
   file { "${android::installdir}/expect-install-${title}":
     content => template('android/expect-script.erb'),
     mode    => '0755',
@@ -59,8 +100,10 @@
   exec { "update-android-package-${title}":
     command => "${android::installdir}/expect-install-${title}",
     creates => $creates,
+    onlyif  => $onlyif,
+    path    => ['/bin', '/usr/bin'],  # For grep.
     timeout => 0,
-    require => [Class['android::sdk']],
+    unless  => $unless,
+    require => Class['android::sdk'],
   }
-
 }
diff --git a/manifests/paths.pp b/manifests/paths.pp
index b8772d3..03a2cc3 100644
--- a/manifests/paths.pp
+++ b/manifests/paths.pp
@@ -1,7 +1,7 @@
-# === Class: android::paths
+# == Class: android::paths
 #
-# This class defines the paths used in the Android SDK installation
-# and operation.
+# This class defines the paths used in the Android SDK installation and
+# operation.
 #
 # === Authors
 #
diff --git a/manifests/platform.pp b/manifests/platform.pp
index 4640e3d..eb8d2b2 100644
--- a/manifests/platform.pp
+++ b/manifests/platform.pp
@@ -2,6 +2,16 @@
 #
 # Installs an Android SDK platform package.
 #
+# === Examples
+#
+# To install a platform package:
+#   android::platform { 'android-16': }
+#
+# === Parameters
+#
+# [*revision*] The revision number of the specified platform package or a value
+#   of 'latest' or 'present'
+#
 # === Authors
 #
 # Etienne Pelletier <epelletier@maestrodev.com>
@@ -10,10 +20,12 @@
 #
 # Copyright 2012 MaestroDev, unless otherwise noted.
 #
-define android::platform() {
+define android::platform(
+  $revision = 'present',
+) {
 
-  android::package{ $title:
-    type => 'platform',
+  android::package { $title:
+    revision => $revision,
+    type     => 'platform',
   }
-
 }
diff --git a/manifests/platform_tools.pp b/manifests/platform_tools.pp
index 00b3f5f..0d1ac93 100644
--- a/manifests/platform_tools.pp
+++ b/manifests/platform_tools.pp
@@ -12,8 +12,7 @@
 #
 class android::platform_tools {
 
-  android::package{ 'platform-tools':
+  android::package { 'platform-tools':
     type => 'platform-tools',
   }
-
 }
diff --git a/manifests/sdk.pp b/manifests/sdk.pp
index 4e4effd..1640d09 100644
--- a/manifests/sdk.pp
+++ b/manifests/sdk.pp
@@ -1,7 +1,7 @@
 # == Class: android::sdk
 #
-# This downloads and unpacks the Android SDK. It also
-# installs necessary 32bit libraries for 64bit Linux systems.
+# This downloads and unpacks the Android SDK. It also installs the necessary
+# 32-bit libraries for 64-bit Linux systems.
 #
 # === Authors
 #
@@ -12,6 +12,7 @@
 # Copyright 2012 MaestroDev, unless otherwise noted.
 #
 class android::sdk {
+
   include android::paths
   include wget
 
@@ -44,27 +45,32 @@
     command => $unpack_command,
     creates => $android::paths::sdk_home,
     cwd     => $android::paths::installdir,
-  }->
+  } ->
   file { 'android-executable':
-    ensure => present,
+    ensure => file,
     path   => "${android::paths::toolsdir}/android",
     owner  => $android::user,
     group  => $android::group,
     mode   => '0755',
   }
 
-  # For 64bit systems, we need to install some 32bit libraries for the SDK
+  # For 64-bit systems, we need to install some 32-bit libraries for the SDK
   # to work.
-  if ($::kernel == 'Linux') and ($::architecture == 'x86_64' or $::architecture == 'amd64') {
-    if $::lsbdistcodename == 'jessie' or $::lsbdistrelease == 14.04 {
-      ensure_packages(['libc6-i386', 'lib32stdc++6', 'lib32gcc1', 'lib32ncurses5', 'lib32z1'])
-    } else {
-      ensure_packages($::osfamily ? {
-        # list 64-bit version and use latest for installation too so that the same version is applied to both
-        'RedHat' => ['glibc.i686','zlib.i686','libstdc++.i686','zlib','libstdc++'],
-        'Debian' => ['ia32-libs'],
-        default  => [],
-      })
-    }
+  if ($::kernel == 'Linux') and ($::architecture == 'x86_64' or $::architecture == 'amd64')
+    and ($::lsbdistid != 'Ubuntu' or versioncmp($::lsbdistrelease, '14.04') < 0)
+    and ($::lsbdistid != 'Debian' or versioncmp($::lsbdistrelease, '7.0') < 0) {
+    ensure_packages($::osfamily ? {
+      # List 64-bit version and use latest for installation too so that the same
+      # version is applied to both.
+      'RedHat' => ['glibc.i686', 'zlib.i686', 'libstdc++.i686', 'zlib', 'libstdc++'],
+      'Debian' => ['ia32-libs'],
+      default  => [],
+    })
+  }
+
+  if ($::lsbdistid == 'Ubuntu' and versioncmp($::lsbdistrelease, '14.04') >= 0)
+    or ($::lsbdistid == 'Debian' and versioncmp($::lsbdistrelease, '7.0') >= 0) {
+
+    ensure_packages(['libc6-i386', 'lib32stdc++6', 'lib32gcc1', 'lib32ncurses5', 'lib32z1'])
   }
 }
diff --git a/manifests/system_images.pp b/manifests/system_images.pp
index 67d0aa5..95aaaf1 100644
--- a/manifests/system_images.pp
+++ b/manifests/system_images.pp
@@ -1,6 +1,16 @@
-# == Class: android::system_images
+# == Define: android::system_images
 #
-# Installs the Android SDK system-images.
+# Installs an Android SDK system image package.
+#
+# === Examples
+#
+# To install a system image package:
+#   android::system_images { 'sys-img-armeabi-v7a-android-23': }
+#
+# === Parameters
+#
+# [*revision*] The revision number of the specified system image package or a
+#   value of 'latest' or 'present'
 #
 # === Authors
 #
@@ -8,12 +18,14 @@
 #
 # === Copyright
 #
-# Copyright 2013 Philip Schiffer
+# Copyright 2013 Philip Schiffer, unless otherwise noted.
 #
-define android::system_images() {
+define android::system_images(
+  $revision = 'present',
+) {
 
-  android::package{ $title:
-    type => 'system-images',
+  android::package { $title:
+    revision => $revision,
+    type     => 'system-images',
   }
-
 }
diff --git a/metadata.json b/metadata.json
index 42d275c..8fd7d3d 100644
--- a/metadata.json
+++ b/metadata.json
@@ -2,12 +2,12 @@
   "name": "maestrodev-android",
   "version": "1.3.2",
   "author": "maestrodev",
-  "summary": "Android SDK module for Puppet",
+  "summary": "Android SDK and NDK module for Puppet",
   "license": "Apache-2.0",
   "source": "http://github.com/maestrodev/puppet-android",
   "project_page": "http://github.com/maestrodev/puppet-android",
   "issues_url": "https://github.com/maestrodev/puppet-android/issues",
-  "description": "A Puppet module to install the Android SDK.",
+  "description": "A Puppet module to install the Android SDK and NDK.",
   "dependencies": [
     {
       "name": "maestrodev/wget",
@@ -65,7 +65,8 @@
       "operatingsystem": "Debian",
       "operatingsystemrelease": [
         "6",
-        "7"
+        "7",
+        "8"
       ]
     },
     {
@@ -97,7 +98,9 @@
         "10",
         "11",
         "12",
-        "13"
+        "13",
+        "14",
+        "15"
       ]
     }
   ],
diff --git a/spec/acceptance/android_system_spec.rb b/spec/acceptance/android_system_spec.rb
index 7bbc914..1af66f4 100644
--- a/spec/acceptance/android_system_spec.rb
+++ b/spec/acceptance/android_system_spec.rb
@@ -1,6 +1,6 @@
-require "spec_helper_acceptance"
+require 'spec_helper_acceptance'
 
-describe "android" do
+describe 'android' do
 
   let(:manifest) {
     %Q{
@@ -14,8 +14,8 @@ class { 'android': }
     }
   }
 
-  it "android SDK should install" do
-    # Run it twice and test for idempotency
+  it 'android SDK should install' do
+    # Run it twice and test for idempotency.
     apply_manifest(manifest, :catch_failures => true)
     apply_manifest(manifest, :catch_changes => true)
   end
diff --git a/spec/classes/init_spec.rb b/spec/classes/init_spec.rb
index ff3e217..b622068 100644
--- a/spec/classes/init_spec.rb
+++ b/spec/classes/init_spec.rb
@@ -1,6 +1,6 @@
 require 'spec_helper'
 
-describe "android" do
+describe 'android' do
   let(:version) { '22.3' }
   let(:dir) { '/usr/local/android' }
   let(:facts) { {
@@ -12,13 +12,13 @@
     it { should contain_class('android::sdk') }
     it { should contain_class('android::platform_tools') }
 
-    it { should contain_Wget__Fetch("download-androidsdk").with({ 
+    it { should contain_Wget__Fetch('download-androidsdk').with({
       :source => "http://dl.google.com/android/android-sdk_r#{version}-linux.tgz",
       :destination => "#{dir}/android-sdk_r#{version}-linux.tgz"})
     }
 
     it { should contain_file("#{dir}/expect-install-platform-tools")
-      .with_content(/android update sdk -u --all -t platform-tools/) }
+      .with_content(/android update sdk -u -a -t platform-tools/) }
     it { should contain_exec('update-android-package-platform-tools')
       .with_command("#{dir}/expect-install-platform-tools") }
 
@@ -31,7 +31,7 @@
     let(:params) { {
       :version => version
     } }
-    it { should contain_Wget__Fetch("download-androidsdk").with({
+    it { should contain_Wget__Fetch('download-androidsdk').with({
       :source => "http://dl.google.com/android/android-sdk_r#{version}-linux.tgz",
       :destination => "#{dir}/android-sdk_r#{version}-linux.tgz"})
     }
@@ -45,7 +45,7 @@
     } }
 
     it { should contain_file("#{dir}/expect-install-platform-tools")
-      .with_content(/android update sdk -u --all -t platform-tools --proxy-host myhost --proxy-port 1234/) }
+      .with_content(/android update sdk -u -a -t platform-tools --proxy-host myhost --proxy-port 1234/) }
     it { should contain_exec('update-android-package-platform-tools')
       .with_command("#{dir}/expect-install-platform-tools") }
   end
@@ -92,13 +92,13 @@
       :proxy_port => '1234'
     } }
 
-    it { should contain_Wget__Fetch("download-androidsdk").with({
+    it { should contain_Wget__Fetch('download-androidsdk').with({
       :source => "http://dl.google.com/android/android-sdk_r#{version}-macosx.zip",
       :destination => "#{dir}/android-sdk_r#{version}-macosx.zip"})
     }
 
     it { should contain_file("#{dir}/expect-install-platform-tools")
-      .with_content(/android update sdk -u --all -t platform-tools --proxy-host myhost --proxy-port 1234/) }
+      .with_content(/android update sdk -u -a -t platform-tools --proxy-host myhost --proxy-port 1234/) }
     it { should contain_exec('update-android-package-platform-tools')
       .with_command("#{dir}/expect-install-platform-tools") }
 
diff --git a/spec/classes/ndk_spec.rb b/spec/classes/ndk_spec.rb
index 3ca6abc..597350e 100644
--- a/spec/classes/ndk_spec.rb
+++ b/spec/classes/ndk_spec.rb
@@ -1,6 +1,6 @@
 require 'spec_helper'
 
-describe "android::ndk" do
+describe 'android::ndk' do
 
     let(:pre_condition) { 'include android' }
 
diff --git a/spec/classes/sdk_spec.rb b/spec/classes/sdk_spec.rb
index caed826..2906231 100644
--- a/spec/classes/sdk_spec.rb
+++ b/spec/classes/sdk_spec.rb
@@ -1,6 +1,6 @@
 require 'spec_helper'
 
-describe "android::sdk" do
+describe 'android::sdk' do
   let(:pre_condition) { 'include android' }
 
   context '64bit RedHat', :compile do
diff --git a/spec/defines/build_tools_spec.rb b/spec/defines/build_tools_spec.rb
new file mode 100644
index 0000000..a74e5d9
--- /dev/null
+++ b/spec/defines/build_tools_spec.rb
@@ -0,0 +1,7 @@
+require 'spec_helper'
+
+describe 'android::build_tools', :compile do
+
+  let(:title) { 'build-tools-19.0.1' }
+
+end
diff --git a/spec/defines/package_spec.rb b/spec/defines/package_spec.rb
index 772308e..6206e3b 100644
--- a/spec/defines/package_spec.rb
+++ b/spec/defines/package_spec.rb
@@ -8,7 +8,7 @@
     let(:title) { 'android-15' }
     let(:params) { { :type => 'platform' } }
     it { should contain_file("#{dir}/expect-install-android-15")
-      .with_content(/android update sdk -u --all -t android-15/) }
+      .with_content(/android update sdk -u -a -t android-15/) }
     it { should contain_exec('update-android-package-android-15').with({
       :command => "#{dir}/expect-install-android-15",
       :creates => "#{dir}/android-sdk-linux/platforms/android-15",
@@ -21,8 +21,8 @@
     
     it do
       expect {
-        should contain_exec('update-android-package-bad') 
-      }.to raise_error(Puppet::Error, /Unsupported package type: bad/) 
+        should raise_error(Puppet::Error, /Unsupported package type: bad/)
+      }
     end
   end
   
@@ -32,7 +32,7 @@
     } }
     let(:title) { 'android-15' }
     let(:params) { { :type => 'platform' } }
-    it { should contain_file("#{dir}/expect-install-android-15").with_content(/android update sdk -u --all -t android-15/) }
+    it { should contain_file("#{dir}/expect-install-android-15").with_content(/android update sdk -u -a -t android-15/) }
     it { should contain_exec('update-android-package-android-15').with({
       :command => "#{dir}/expect-install-android-15",
       :creates => "#{dir}/android-sdk-macosx/platforms/android-15",
diff --git a/spec/defines/system_images.rb b/spec/defines/system_images.rb
new file mode 100644
index 0000000..db7568b
--- /dev/null
+++ b/spec/defines/system_images.rb
@@ -0,0 +1,7 @@
+require 'spec_helper'
+
+describe 'android::system_images', :compile do
+
+  let(:title) { 'sys-img-armeabi-v7a-android-23' }
+
+end
diff --git a/templates/expect-script.erb b/templates/expect-script.erb
index e2b84f1..a12fe24 100755
--- a/templates/expect-script.erb
+++ b/templates/expect-script.erb
@@ -3,14 +3,28 @@
 require 'pty'
 require 'expect'
 
-command="<%= scope.lookupvar('android::paths::sdk_home') %>/tools/android update sdk -u --all -t <%= @title %> <%= @proxy_host %> <%= @proxy_port %>"
-match=%r/^\s*Do you accept the license .* \[y\/n\]:\s*/
-response="y"
+command = "<%= scope.lookupvar('android::paths::sdk_home') %>/tools/android update sdk -u -a -t <%= @title %> <%= @proxy_host %> <%= @proxy_port %>"
 
-puts command
+dry_mode_command = "#{command} -n"
+dry_mode_match = %r/^\s*Error: Ignoring unknown package filter '<%= @title %>'\s*/
 
-PTY.spawn(command) do |r,w,p|
+puts dry_mode_command
 
+PTY.spawn(dry_mode_command) do |r, w, pid|
+  begin
+    r.expect(dry_mode_match) do |result|
+      exit 1 unless result.nil?
+    end
+  rescue Errno::EIO, PTY::ChildExited
+  end
+end
+
+match = %r/^\s*Do you accept the license .* \[y\/n\]:\s*/
+response = 'y'
+
+puts command
+
+PTY.spawn(command) do |r, w, pid|
   w.sync = true
 
   begin
@@ -24,4 +38,5 @@ PTY.spawn(command) do |r,w,p|
 end
 
 exit
+
 #  vim: set ts=2 sw=2 tw=0 et: