Merge pull request #10775 from senny/postgres_adapter_test_cleanup

test cleanup, replace `define_method` and `remove_method` with stubs.

activerecord/test/cases/adapters/postgresql/active_schema_test.rb

@@ -25,9 +25,7 @@ def test_create_database_with_collation_and_ctype
 
   def test_add_index
     # add_index calls index_name_exists? which can't work since execute is stubbed
-    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.send(:define_method, :index_name_exists?) do |*|
-      false
-    end
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.stubs(:index_name_exists?).returns(false)
 
     expected = %(CREATE UNIQUE INDEX  "index_people_on_last_name" ON "people"  ("last_name") WHERE state = 'active')
     assert_equal expected, add_index(:people, :last_name, :unique => true, :where => "state = 'active'")
@@ -51,8 +49,6 @@ def test_add_index
 
     expected = %(CREATE UNIQUE INDEX  "index_people_on_last_name" ON "people" USING gist ("last_name") WHERE state = 'active')
     assert_equal expected, add_index(:people, :last_name, :unique => true, :where => "state = 'active'", :using => :gist)
-
-    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.send(:remove_method, :index_name_exists?)
   end
 
   private