Send success email to merged users

app/mailers/merge_completion_mailer.rb

@@ -0,0 +1,17 @@
+class MergeCompletionMailer < NotifyMailer
+  MERGE_COMPLETION_TEMPLATE_ID = "xxx".freeze
+
+  def send_merge_completion_mail(email, merged_organisation_name, absorbing_organisation_name, merge_date, username)
+    send_email(
+      email,
+      MERGE_COMPLETION_TEMPLATE_ID,
+      {
+        merged_organisation_name:,
+        absorbing_organisation_name:,
+        merge_date:,
+        email:,
+        username:,
+      },
+    )
+  end
+end

app/services/merge/merge_organisations_service.rb

@@ -22,6 +22,7 @@ class Merge::MergeOrganisationsService
       end
       @absorbing_organisation.available_from = @merge_date if @absorbing_organisation_active_from_merge_date
       @absorbing_organisation.save!
+      send_success_emails
       log_success_message
     rescue ActiveRecord::RecordInvalid => e
       Rails.logger.error("Organisation merge failed with: #{e.message}")
@@ -151,6 +152,14 @@ private
     end
   end
 
+  def send_success_emails
+    @merged_users.each do |organisation_name, users|
+      users.each do |user|
+        MergeCompletionMailer.send_merge_completion_mail(user[:email], organisation_name, @absorbing_organisation.name, @merge_date, user[:name]).deliver_later
+      end
+    end
+  end
+
   def merge_boolean_organisation_attribute(attribute)
     @absorbing_organisation[attribute] ||= @merging_organisations.any? { |merging_organisation| merging_organisation[attribute] }
   end

spec/mailers/merge_completion_mailer_spec.rb

@@ -0,0 +1,26 @@
+require "rails_helper"
+
+RSpec.describe MergeCompletionMailer do
+  let(:notify_client) { instance_double(Notifications::Client) }
+
+  before do
+    allow(Notifications::Client).to receive(:new).and_return(notify_client)
+    allow(notify_client).to receive(:send_email).and_return(true)
+  end
+
+  describe "#send_merge_completion_mail" do
+    let(:merge_date) { Time.zone.today }
+
+    it "sends a merge completion E-mail via notify" do
+      expect(notify_client).to receive(:send_email).with(hash_including({ personalisation: hash_including({
+        merged_organisation_name: "merged organisation",
+        absorbing_organisation_name: "absorbing organisation",
+        merge_date:,
+        email: "user@example.com",
+        username: "user",
+      }) }))
+
+      described_class.new.send_merge_completion_mail("user@example.com", "merged organisation", "absorbing organisation", merge_date, "user")
+    end
+  end
+end

spec/services/merge/merge_organisations_service_spec.rb

@@ -2,10 +2,15 @@ require "rails_helper"
 
 RSpec.describe Merge::MergeOrganisationsService do
   describe "#call" do
+    before do
+      mail_double = instance_double("ActionMailer::MessageDelivery", deliver_later: nil)
+      allow(MergeCompletionMailer).to receive(:send_merge_completion_mail).and_return(mail_double)
+    end
+
     context "when merging a single organisation into an existing organisation" do
       subject(:merge_organisations_service) { described_class.new(absorbing_organisation_id: absorbing_organisation.id, merging_organisation_ids: [merging_organisation_ids], merge_date: nil) }
 
-      let(:absorbing_organisation) { create(:organisation, holds_own_stock: false) }
+      let(:absorbing_organisation) { create(:organisation, holds_own_stock: false, name: "absorbing org") }
       let(:absorbing_organisation_user) { create(:user, organisation: absorbing_organisation) }
 
       let(:merging_organisation) { create(:organisation, holds_own_stock: true, name: "fake org") }
@@ -831,6 +836,13 @@ RSpec.describe Merge::MergeOrganisationsService do
           expect(absorbing_organisation.available_from.to_date).to eq(Time.zone.today)
         end
       end
+
+      it "sends a merge completion E-mail to the merged organisation users" do
+        expect(MergeCompletionMailer).to receive(:send_merge_completion_mail).with(merging_organisation_user.email, "fake org", "absorbing org", Time.zone.today, merging_organisation_user.name).once
+        expect(MergeCompletionMailer).to receive(:send_merge_completion_mail).with(merging_organisation.data_protection_officers.first.email, "fake org", "absorbing org", Time.zone.today, merging_organisation.data_protection_officers.first.name).once
+
+        merge_organisations_service.call
+      end
     end
 
     context "when merging a multiple organisations into an existing organisation" do