add actionmailer test coverage for undefined delivery method

actionmailer/lib/action_mailer/base.rb

@@ -764,7 +764,7 @@ def mail(headers = {}, &block)
       m.charset = charset = headers[:charset]
 
       # Set configure delivery behavior
-      wrap_delivery_behavior!(headers.delete(:delivery_method),headers.delete(:delivery_method_options))
+      wrap_delivery_behavior!(headers.delete(:delivery_method), headers.delete(:delivery_method_options))
 
       # Assign all headers except parts_order, content_type and body
       assignable = headers.except(:parts_order, :content_type, :body, :template_name, :template_path)

actionmailer/test/delivery_methods_test.rb

@@ -38,8 +38,10 @@ class DefaultsDeliveryMethodsTest < ActiveSupport::TestCase
   end
 
   test "default sendmail settings" do
-    settings = {location:  '/usr/sbin/sendmail',
-                arguments: '-i -t'}
+    settings = {
+      location:  '/usr/sbin/sendmail',
+      arguments: '-i -t'
+    }
     assert_equal settings, ActionMailer::Base.sendmail_settings
   end
 end
@@ -138,13 +140,15 @@ def teardown
   end
 
   test "default delivery options can be overridden per mail instance" do
-    settings = { address:              "localhost",
-                 port:                 25,
-                 domain:               'localhost.localdomain',
-                 user_name:            nil,
-                 password:             nil,
-                 authentication:       nil,
-                 enable_starttls_auto: true }
+    settings = {
+      address: "localhost",
+      port: 25,
+      domain: 'localhost.localdomain',
+      user_name: nil,
+      password: nil,
+      authentication: nil,
+      enable_starttls_auto: true
+    }
     assert_equal settings, ActionMailer::Base.smtp_settings
     overridden_options = {user_name: "overridden", password: "somethingobtuse"}
     mail_instance = DeliveryMailer.welcome(delivery_method_options: overridden_options)
@@ -164,6 +168,13 @@ def teardown
     end
   end
 
+  test "undefined delivery methods raises errors" do
+    DeliveryMailer.delivery_method = nil
+    assert_raise RuntimeError do
+      DeliveryMailer.welcome.deliver
+    end
+  end
+
   test "does not perform deliveries if requested" do
     DeliveryMailer.perform_deliveries = false
     DeliveryMailer.deliveries.clear