Make replace_nameservers return an array of domain names

app/models/registrar.rb

@@ -132,14 +132,20 @@ class Registrar < ActiveRecord::Base
   # Audit log is needed, therefore no raw SQL
   def replace_nameservers(hostname, new_attributes)
     transaction do
+      domain_list = []
+
       nameservers.where(hostname: hostname).find_each do |original_nameserver|
         new_nameserver = Nameserver.new
         new_nameserver.domain = original_nameserver.domain
         new_nameserver.attributes = new_attributes
         new_nameserver.save!
 
+        domain_list << original_nameserver.domain.name
+
         original_nameserver.destroy!
       end
+
+      domain_list
     end
   end
 

test/models/registrar/replace_nameservers_test.rb

@@ -0,0 +1,23 @@
+require 'test_helper'
+
+class ReplaceNameserversTest < ActiveSupport::TestCase
+  def setup
+    @registrar = registrars(:bestnames)
+  end
+
+  def test_replace_nameservers_in_bulk_returns_domain_names
+    new_attributes = { hostname: 'ns-updated1.bestnames.test', ipv4: '192.0.3.1',
+                       ipv6: '2001:db8::2' }
+    result = @registrar.replace_nameservers('ns1.bestnames.test', new_attributes)
+
+    assert_equal(["airport.test", "shop.test"], result)
+  end
+
+  def test_replace_nameservers_in_bulk_returns_empty_array_for_non_existent_base_nameserver
+    new_attributes = { hostname: 'ns-updated1.bestnames.test', ipv4: '192.0.3.1',
+                       ipv6: '2001:db8::2' }
+    result = @registrar.replace_nameservers('ns3.bestnames.test', new_attributes)
+
+    assert_equal([], result)
+  end
+end