SL add rspec matcher

README.md

@@ -379,3 +379,14 @@ MandrillMailer.configure do |config|
   }
 end
 ```
+
+## Rspec matcher
+
+# In spec/spec_helper.rb:
+```ruby
+  RSpec.configure do |config|
+    # ...
+    require "mandrill_mailer/rspec_helper"
+    config.include MandrillMailer::RSpecHelper
+  end
+```

lib/mandrill_mailer/rspec_helper.rb

@@ -37,5 +37,6 @@ module RSpecHelper
     require 'mandrill_mailer/rspec_helpers/subject_matcher'
     require 'mandrill_mailer/rspec_helpers/template_matcher'
     require 'mandrill_mailer/rspec_helpers/to_email_matcher'
+    require 'mandrill_mailer/rspec_helpers/mandrill_mailer_contains'
   end
 end

lib/mandrill_mailer/rspec_helpers/mandrill_mailer_contains.rb

@@ -0,0 +1,113 @@
+# frozen_string_literal: true
+#
+# Public: Matcher for asserting :template_name, receiver_email - :to, and optional global variables
+#
+# WelcomeMailer is an instance of MandrillMailler::TemplateMailer
+#
+# mail = MandrillMailer.deliveries.last
+#
+# expect(mail).to be_mandrill_email(
+#   template_name: 'user-registered-for-event',
+#   to: '[email protected]'
+# )
+#
+#  expect(MandrillMailer.deliveries).to include(
+#    mandrill_email(
+#      template_name: 'user-registered-for-event',
+#      to: '[email protected]'
+#    ),
+#    mandrill_email(
+#      template_name: 'send-invitation-to-user',
+#      to: '[email protected]'
+#    ),
+#    mandrill_email(
+#      template_name: 'send-invitation-to-user',
+#      to: '[email protected]'
+#    ),
+#    mandrill_email(
+#      template_name: 'send-invitation-and-paid',
+#      to: '[email protected]'
+#    ),
+#  )
+# expect(mailer).to be_mandrill_email(
+#  template_name: 'user-registered-for-event',
+#  to: '[email protected]',
+#  global_variables: {
+#    'FNAME' => 'John',
+#    'START_TIME' => '10:45am EST / 7:45am PST',
+#    'VENUE' => 'Midtown Venue',
+#    'START_DATE' => 'Wednesday, 01/10/2018',
+#    'NEXT_EVENT_DATE' => nil,
+#    'MEMBER_FULL_NAME' => 'John Gates',
+#    'MEMBER_EMAIL' => '[email protected]'
+#  }
+# )
+#
+RSpec::Matchers.define :mandrill_email do |expected|
+  class MailerContains < RSpec::Matchers::BuiltIn::BaseMatcher
+    attr_reader :errors
+
+    def initialize(expected, actual)
+      @expected = expected
+      @actual = actual
+      @errors = []
+    end
+
+    def self.check(expected, actual)
+      new(expected, actual).check
+    end
+
+    def check
+      @errors << not_match_template_name if actual.template_name != expected.fetch(:template_name)
+      @errors << not_match_receiver if actual.message['to'].first['email'] != expected.fetch(:to)
+      check_global_variables if expected[:global_variables].present?
+      self
+    end
+
+    def check_global_variables
+      expected_global_variables = expected.fetch(:global_variables)
+      @errors << variable_missing if (expected_global_variables.to_a - actual_global_variables.to_a).any?
+    end
+
+    def actual_global_variables
+      actual.message['global_merge_vars'].map(&:values).to_h
+    end
+
+    def variable_missing
+      "Global variables missing. Expected: #{expected.fetch(:global_variables)}, got: #{actual_global_variables}" + differ.diff_as_object(expected.fetch(:global_variables), actual_global_variables)
+    end
+
+    def not_match_template_name
+      "Template name doesn't match. Expected: #{expected.fetch(:template_name)}, got: #{actual.template_name}" + differ.diff_as_string(expected.fetch(:template_name), actual.template_name)
+    end
+
+    def not_match_receiver
+      "Receiver doesn't match. Expected: #{expected.fetch(:to)}, got: #{actual.message['to'].first['email']}" + differ.diff_as_string(expected.fetch(:to), actual.message['to'].first['email'])
+    end
+
+    def differ
+      RSpec::Support::Differ.new(object_preparer: ->(object) { RSpec::Matchers::Composable.surface_descriptions_in(object) }, color: RSpec::Matchers.configuration.color?
+      )
+    end
+
+    private
+
+    attr_reader :expected, :actual
+  end
+
+  match do |actual|
+    matcher = MailerContains.check(expected, actual)
+    if matcher.errors.present?
+      @failure_message = matcher.errors.join("\n")
+      return false
+    end
+
+    true
+  end
+
+  failure_message do
+    @failure_message
+  end
+end
+
+RSpec::Matchers.alias_matcher :be_mandrill_email, :mandrill_email