Add tests for Mailer support

decent_exposure.gemspec

@@ -24,5 +24,6 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency "activesupport", ">= 4.0"
   spec.add_development_dependency "railties", ">= 4.0"
+  spec.add_development_dependency "actionmailer"
   spec.add_development_dependency "rspec-rails", "~> 3.0"
 end

spec/features/birds_mailer_spec.rb

@@ -0,0 +1,46 @@
+require "spec_helper"
+require "support/rails_app"
+require "rspec/rails"
+require "action_mailer"
+
+class BirdsMailer < ActionMailer::Base
+end
+
+RSpec.describe BirdsMailer, type: :mailer do
+  let(:bird){ double :bird }
+  let(:birds) { double :birds }
+
+  context "when birds relation is exposed" do
+    class BirdsMailer
+      expose(:birds, -> { Bird.all })
+
+      def hello_birds
+        mail { |format| format.text { render plain: "Hello #{birds}" } }
+      end
+    end
+
+    it "sends the email with exposed birds" do
+      expect(Bird).to receive(:all).and_return(birds)
+      expect(described_class.hello_birds.body.to_s)
+        .to include("Hello #{birds}")
+    end
+  end
+
+  context "when bird is exposed" do
+    class BirdsMailer
+      attr_accessor :bird_id
+      expose(:bird, id: -> { bird_id })
+
+      def hello_bird(id)
+        self.bird_id = id
+        mail { |format| format.text { render plain: "Hello #{bird}" } }
+      end
+    end
+
+    it "sends the email with exposed bird" do
+      expect(Bird).to receive(:find).with('some-id').and_return(bird)
+      expect(described_class.hello_bird('some-id').body.to_s)
+        .to include("Hello #{bird}")
+    end
+  end
+end

spec/support/rails_app.rb

@@ -23,6 +23,10 @@ def routes
     end
   end
 
+  def self.root
+    ''
+  end
+
   def self.application
     @app ||= App.new
   end