diff --git a/.fixtures.yml b/.fixtures.yml
index 63f3809..839ed5f 100644
--- a/.fixtures.yml
+++ b/.fixtures.yml
@@ -2,6 +2,8 @@ fixtures:
   repositories:
     stdlib:
       repo: "git://github.com/puppetlabs/puppetlabs-stdlib"
-      ref: "4.3.2"
+      ref: "a656880f13cc13a30baa892dcc4c8e3efefcc867"
+    reboot: "git://github.com/puppetlabs/puppetlabs-reboot"
+    powershell: "git://github.com/puppetlabs/puppetlabs-powershell"
   symlinks:
     domain_membership: "#{source_dir}"
diff --git a/tests/init.pp b/examples/init.pp
similarity index 100%
rename from tests/init.pp
rename to examples/init.pp
diff --git a/manifests/init.pp b/manifests/init.pp
index 167b75b..0afb1dd 100644
--- a/manifests/init.pp
+++ b/manifests/init.pp
@@ -52,9 +52,9 @@
 #
 class domain_membership (
   Stdlib::Fqdn $domain,
-  Optional[Stdlib::Fqdn] $user_domain,
   String $username,
   String $password,
+  Optional[Stdlib::Fqdn] $user_domain           = undef,
   Boolean $secure_password                      = false,
   String $machine_ou                            = '$null',
   Boolean $resetpw                              = true,
@@ -72,15 +72,16 @@
 
   # Allow an optional user_domain to accomodate multi-domain AD forests
   if $user_domain {
+    $_user_domain = $user_domain
     $_reset_username = "${user_domain}\\${username}"
   } else {
-    $user_domain = $domain
+    $_user_domain = $domain
     $_reset_username = $username
   }
 
   exec { 'join_domain':
     environment => [ "Password=${_password}" ],
-    command     => "exit (Get-WmiObject -Class Win32_ComputerSystem).JoinDomainOrWorkGroup('${domain}',\$Password,'${username}@${user_domain}',${machine_ou},${join_options}).ReturnValue",
+    command     => "exit (Get-WmiObject -Class Win32_ComputerSystem).JoinDomainOrWorkGroup('${domain}',\$Password,'${username}@${_user_domain}',${machine_ou},${join_options}).ReturnValue",
     unless      => "if((Get-WmiObject -Class Win32_ComputerSystem).domain -ne '${domain}'){ exit 1 }",
     provider    => powershell,
   }
diff --git a/spec/classes/init_spec.rb b/spec/classes/init_spec.rb
new file mode 100644
index 0000000..a8a1396
--- /dev/null
+++ b/spec/classes/init_spec.rb
@@ -0,0 +1,19 @@
+require 'spec_helper'
+require 'puppetlabs_spec_helper/module_spec_helper'
+
+describe 'domain_membership' do
+  on_supported_os.each do |os, facts|
+    context "on #{os}" do
+      let(:facts) { facts }
+      let(:params) do
+        {
+          domain: 'test.domain',
+          username: 'testuser',
+          password: 'password1',
+        }
+      end
+
+      it { is_expected.to compile.with_all_deps }
+    end
+  end
+end