add missing require to have_enqueued_mail (#2117)

features/matchers/have_enqueued_mail_matcher.feature

@@ -0,0 +1,78 @@
+Feature: have_enqueued_mail matcher
+
+  The `have_enqueued_mail` (also aliased as `enqueue_mail`) matcher is used to check if given mailer was enqueued.
+
+  Background:
+    Given active job is available
+
+  @rails_post_5
+  Scenario: Checking mailer class and method name
+    Given a file named "spec/mailers/user_mailer_spec.rb" with:
+      """ruby
+      require "rails_helper"
+
+      RSpec.describe NotificationsMailer do
+        it "matches with enqueued mailer" do
+          ActiveJob::Base.queue_adapter = :test
+          expect {
+            NotificationsMailer.signup.deliver_later
+          }.to have_enqueued_mail(NotificationsMailer, :signup)
+        end
+      end
+      """
+    When I run `rspec spec/mailers/user_mailer_spec.rb`
+    Then the examples should all pass
+
+  @rails_post_5
+  Scenario: Checking mailer enqueued time
+    Given a file named "spec/mailers/user_mailer_spec.rb" with:
+      """ruby
+      require "rails_helper"
+
+      RSpec.describe NotificationsMailer do
+        it "matches with enqueued mailer" do
+          ActiveJob::Base.queue_adapter = :test
+          expect {
+            NotificationsMailer.signup.deliver_later(:wait_until => Date.tomorrow.noon)
+          }.to have_enqueued_mail.at(Date.tomorrow.noon)
+        end
+      end
+      """
+    When I run `rspec spec/mailers/user_mailer_spec.rb`
+    Then the examples should all pass
+
+  @rails_pre_5
+  Scenario: Checking mailer class and method name
+    Given a file named "spec/mailers/user_mailer_spec.rb" with:
+      """ruby
+      require "rails_helper"
+
+      RSpec.describe Notifications do
+        it "matches with enqueued mailer" do
+          ActiveJob::Base.queue_adapter = :test
+          expect {
+            Notifications.signup.deliver_later
+          }.to have_enqueued_mail(Notifications, :signup)
+        end
+      end
+      """
+    When I run `rspec spec/mailers/user_mailer_spec.rb`
+    Then the examples should all pass
+
+  @rails_pre_5
+  Scenario: Checking mailer enqueued time
+    Given a file named "spec/mailers/user_mailer_spec.rb" with:
+      """ruby
+      require "rails_helper"
+
+      RSpec.describe Notifications do
+        it "matches with enqueued mailer" do
+          ActiveJob::Base.queue_adapter = :test
+          expect {
+            Notifications.signup.deliver_later(:wait_until => Date.tomorrow.noon)
+          }.to have_enqueued_mail.at(Date.tomorrow.noon)
+        end
+      end
+      """
+    When I run `rspec spec/mailers/user_mailer_spec.rb`
+    Then the examples should all pass

lib/rspec/rails/matchers.rb

@@ -22,4 +22,5 @@ module Matchers
 require 'rspec/rails/matchers/have_http_status'
 if RSpec::Rails::FeatureCheck.has_active_job?
   require 'rspec/rails/matchers/active_job'
+  require 'rspec/rails/matchers/have_enqueued_mail'
 end