Add UserMailer specs adapted from Spree code

spec/mailers/user_mailer_spec.rb

@@ -2,7 +2,7 @@ require 'spec_helper'
 
 describe Spree::UserMailer do
   let(:user) { build(:user) }
-  
+
   after do
     ActionMailer::Base.deliveries.clear
   end
@@ -17,4 +17,37 @@ describe Spree::UserMailer do
     Spree::UserMailer.signup_confirmation(user).deliver
     ActionMailer::Base.deliveries.count.should == 1
   end
+
+  # adapted from https://github.com/spree/spree_auth_devise/blob/70737af/spec/mailers/user_mailer_spec.rb
+  describe '#reset_password_instructions' do
+    describe 'message contents' do
+      before do
+        @message = described_class.reset_password_instructions(user)
+      end
+
+      context 'subject includes' do
+        it 'translated devise instructions' do
+          expect(@message.subject).to include "Password Reset Instructions"
+        end
+
+        it 'Spree site name' do
+          expect(@message.subject).to include Spree::Config[:site_name]
+        end
+      end
+
+      context 'body includes' do
+        it 'password reset url' do
+          expect(@message.body.raw_source).to include root_url + "user/spree_user/password/edit"
+        end
+      end
+    end
+
+    describe 'legacy support for User object' do
+      it 'sends an email' do
+        expect do
+          Spree::UserMailer.reset_password_instructions(user).deliver
+        end.to change(ActionMailer::Base.deliveries, :size).by(1)
+      end
+    end
+  end
 end