Send a different email is only one organisation is absorbed

app/mailers/merge_completion_mailer.rb

@@ -1,6 +1,7 @@
 class MergeCompletionMailer < NotifyMailer
   MERGE_COMPLETION_MERGING_ORGANISATION_TEMPLATE_ID = "b3b62e72-5ced-4515-8720-08bdc7bac792".freeze
   MERGE_COMPLETION_ABSORBING_ORGANISATION_TEMPLATE_ID = "7cdfefac-84c3-4054-8bd9-63103b3847b6".freeze
+  ONE_ORG_MERGE_COMPLETION_ABSORBING_ORGANISATION_TEMPLATE_ID = "35456951-2046-468e-9f41-a620e94db203".freeze
 
   def send_merged_organisation_success_mail(email, merged_organisation_name, absorbing_organisation_name, merge_date)
     send_email(
@@ -16,20 +17,30 @@ class MergeCompletionMailer < NotifyMailer
   end
 
   def send_absorbing_organisation_success_mail(email, merged_organisations, absorbing_organisation_name, merge_date)
-    organisation_count = merged_organisations.count.to_s + " organisation".pluralize(merged_organisations.count)
-    pluralised_organisation = merged_organisations.count > 1 ? "these organisations" : "this organisation"
-    merged_organisation_list = (merged_organisations.count > 1 ? "The organisations are " : "The organisation is ") + merged_organisations.to_sentence(last_word_connector: " and ")
+    if merged_organisations.count > 1
+      organisation_count = merged_organisations.count.to_s + " organisation".pluralize(merged_organisations.count)
+      merged_organisation_list = "The organisations are #{merged_organisations.to_sentence(last_word_connector: ' and ')}"
 
-    send_email(
-      email,
-      MERGE_COMPLETION_ABSORBING_ORGANISATION_TEMPLATE_ID,
-      {
-        organisation_count:,
-        merged_organisations: merged_organisation_list,
-        absorbing_organisation_name:,
-        merge_date: merge_date.to_formatted_s(:govuk_date),
-        pluralised_organisation:,
-      },
-    )
+      send_email(
+        email,
+        MERGE_COMPLETION_ABSORBING_ORGANISATION_TEMPLATE_ID,
+        {
+          organisation_count:,
+          merged_organisations: merged_organisation_list,
+          absorbing_organisation_name:,
+          merge_date: merge_date.to_formatted_s(:govuk_date),
+        },
+      )
+    else
+      send_email(
+        email,
+        ONE_ORG_MERGE_COMPLETION_ABSORBING_ORGANISATION_TEMPLATE_ID,
+        {
+          merged_organisation: merged_organisations.first,
+          absorbing_organisation_name:,
+          merge_date: merge_date.to_formatted_s(:govuk_date),
+        },
+      )
+    end
   end
 end

spec/mailers/merge_completion_mailer_spec.rb

@@ -31,13 +31,11 @@ RSpec.describe MergeCompletionMailer do
 
     it "sends a merge completion E-mail via notify for a single merge" do
       expect(notify_client).to receive(:send_email).with(hash_including({
-        template_id: MergeCompletionMailer::MERGE_COMPLETION_ABSORBING_ORGANISATION_TEMPLATE_ID,
+        template_id: MergeCompletionMailer::ONE_ORG_MERGE_COMPLETION_ABSORBING_ORGANISATION_TEMPLATE_ID,
         personalisation: hash_including({
-          organisation_count: "1 organisation",
-          merged_organisations: "The organisation is merged organisation",
+          merged_organisation: "merged organisation",
           absorbing_organisation_name: "absorbing organisation",
           merge_date: "1 January 2023",
-          pluralised_organisation: "this organisation",
         }),
       }))
 
@@ -52,7 +50,6 @@ RSpec.describe MergeCompletionMailer do
           merged_organisations: "The organisations are merged organisation and other organisation",
           absorbing_organisation_name: "absorbing organisation",
           merge_date: "1 January 2023",
-          pluralised_organisation: "these organisations",
         }),
       }))