Add reviewers detail to closed merge request email

app/views/notify/closed_merge_request_email.text.haml

@@ -6,3 +6,4 @@ Merge Request URL: #{project_merge_request_url(@merge_request.target_project, @m
 
 Author: #{sanitize_name(@merge_request.author_name)}
 = assignees_label(@merge_request)
+= reviewers_label(@merge_request)

changelogs/unreleased/300750-add-missing-reviewers-information-to-closed-merge-request-email.yml

+---
+title: Add reviewers detail to text version of closed merge request email
+merge_request: 55594
+author:
+type: added

spec/mailers/emails/merge_requests_spec.rb

@@ -8,7 +8,7 @@ RSpec.describe Emails::MergeRequests do
 
   include_context 'gitlab email notification'
 
-  let_it_be(:current_user) { create(:user) }
+  let_it_be(:current_user, reload: true) { create(:user, email: "current@email.com", name: 'www.example.com') }
   let_it_be(:assignee, reload: true) { create(:user, email: 'assignee@example.com', name: 'John Doe') }
   let_it_be(:reviewer, reload: true) { create(:user, email: 'reviewer@example.com', name: 'Jane Doe') }
   let_it_be(:project) { create(:project, :repository) }
@@ -22,6 +22,39 @@ RSpec.describe Emails::MergeRequests do
   end
 
   let(:recipient) { assignee }
+  let(:current_user_sanitized) { 'www_example_com' }
+
+  describe '#closed_merge_request_email' do
+    subject { Notify.closed_merge_request_email(recipient.id, merge_request.id, current_user.id) }
+
+    it_behaves_like 'an answer to an existing thread with reply-by-email enabled' do
+      let(:model) { merge_request }
+    end
+
+    it_behaves_like 'it should show Gmail Actions View Merge request link'
+    it_behaves_like 'an unsubscribeable thread'
+    it_behaves_like 'appearance header and footer enabled'
+    it_behaves_like 'appearance header and footer not enabled'
+
+    it 'is sent as the author' do
+      sender = subject.header[:from].addrs[0]
+      expect(sender.display_name).to eq(current_user.name)
+      expect(sender.address).to eq(gitlab_sender)
+    end
+
+    it 'has the correct subject and body' do
+      aggregate_failures do
+        is_expected.to have_referable_subject(merge_request, reply: true)
+        is_expected.to have_body_text('closed')
+        is_expected.to have_body_text(current_user_sanitized)
+        is_expected.to have_body_text(project_merge_request_path(project, merge_request))
+        is_expected.to have_link(merge_request.to_reference, href: project_merge_request_url(merge_request.target_project, merge_request))
+
+        expect(subject.text_part).to have_content(assignee.name)
+        expect(subject.text_part).to have_content(reviewer.name)
+      end
+    end
+  end
 
   describe '#merged_merge_request_email' do
     let(:merge_author) { assignee }
@@ -79,7 +112,7 @@ RSpec.describe Emails::MergeRequests do
     subject { Notify.resolved_all_discussions_email(recipient.id, merge_request.id, current_user.id) }
 
     it "includes the name of the resolver" do
-      expect(subject).to have_body_text current_user.name
+      expect(subject).to have_body_text current_user_sanitized
     end
   end