raise exception if location option is not present when setting up del…

…ivery

README.rdoc

@@ -22,7 +22,7 @@ If you aren't using Rails, this can be easily set up with the Mail gem. Just set
 
   require "letter_opener"
   Mail.defaults do
-    delivery_method LetterOpener::DeliveryMethod, :location => "tmp/letter_opener"
+    delivery_method LetterOpener::DeliveryMethod, :location => File.expand_path('../tmp/letter_opener', __FILE__)
   end
 
 

lib/letter_opener/delivery_method.rb

@@ -1,11 +1,14 @@
 module LetterOpener
   class DeliveryMethod
-    def initialize(options = {})
-      self.settings = {:location => './letter_opener'}.merge!(options)
-    end
+    class InvalidOption < StandardError; end
 
     attr_accessor :settings
 
+    def initialize(options = {})
+      raise InvalidOption, "A location option is required when using the Letter Opener delivery method" if options[:location].nil?
+      self.settings = options
+    end
+
     def deliver!(mail)
       location = File.join(settings[:location], "#{Time.now.to_i}_#{Digest::SHA1.hexdigest(mail.encoded)[0..6]}")
       messages = Message.rendered_messages(location, mail)

spec/letter_opener/delivery_method_spec.rb

@@ -13,6 +13,11 @@
     end
   end
 
+  it 'raises an exception if no location passed' do
+    lambda { LetterOpener::DeliveryMethod.new }.should raise_exception(LetterOpener::DeliveryMethod::InvalidOption)
+    lambda { LetterOpener::DeliveryMethod.new(location: "foo") }.should_not raise_exception
+  end
+
   context 'content' do
     let(:plain_file) { Dir["#{location}/*/plain.html"].first }
     let(:plain) { File.read(plain_file) }