1 files changed, 34 insertions, 0 deletions
diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index 17d77c5454..ff7eb86969 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -230,21 +230,41 @@ module ActiveRecord
           @connection.distinct("posts.id", [])
       end
 
+      def test_columns_for_distinct_zero_orders
+        assert_equal "posts.id",
+          @connection.columns_for_distinct("posts.id", [])
+      end
+
       def test_distinct_one_order
         assert_equal "DISTINCT posts.id, posts.created_at AS alias_0",
           @connection.distinct("posts.id", ["posts.created_at desc"])
       end
 
+      def test_columns_for_distinct_one_order
+        assert_equal "posts.id, posts.created_at AS alias_0",
+          @connection.columns_for_distinct("posts.id", ["posts.created_at desc"])
+      end
+
       def test_distinct_few_orders
         assert_equal "DISTINCT posts.id, posts.created_at AS alias_0, posts.position AS alias_1",
           @connection.distinct("posts.id", ["posts.created_at desc", "posts.position asc"])
       end
 
+      def test_columns_for_distinct_few_orders
+        assert_equal "posts.id, posts.created_at AS alias_0, posts.position AS alias_1",
+          @connection.columns_for_distinct("posts.id", ["posts.created_at desc", "posts.position asc"])
+      end
+
       def test_distinct_blank_not_nil_orders
         assert_equal "DISTINCT posts.id, posts.created_at AS alias_0",
           @connection.distinct("posts.id", ["posts.created_at desc", "", "   "])
       end
 
+      def test_columns_for_distinct_blank_not_nil_orders
+        assert_equal "posts.id, posts.created_at AS alias_0",
+          @connection.columns_for_distinct("posts.id", ["posts.created_at desc", "", "   "])
+      end
+
       def test_distinct_with_arel_order
         order = Object.new
         def order.to_sql
@@ -254,11 +274,25 @@ module ActiveRecord
           @connection.distinct("posts.id", [order])
       end
 
+      def test_columns_for_distinct_with_arel_order
+        order = Object.new
+        def order.to_sql
+          "posts.created_at desc"
+        end
+        assert_equal "posts.id, posts.created_at AS alias_0",
+          @connection.columns_for_distinct("posts.id", [order])
+      end
+
       def test_distinct_with_nulls
         assert_equal "DISTINCT posts.title, posts.updater_id AS alias_0", @connection.distinct("posts.title", ["posts.updater_id desc nulls first"])
         assert_equal "DISTINCT posts.title, posts.updater_id AS alias_0", @connection.distinct("posts.title", ["posts.updater_id desc nulls last"])
       end
 
+      def test_columns_for_distinct_with_nulls
+        assert_equal "posts.title, posts.updater_id AS alias_0", @connection.columns_for_distinct("posts.title", ["posts.updater_id desc nulls first"])
+        assert_equal "posts.title, posts.updater_id AS alias_0", @connection.columns_for_distinct("posts.title", ["posts.updater_id desc nulls last"])
+      end
+
       def test_raise_error_when_cannot_translate_exception
         assert_raise TypeError do
           @connection.send(:log, nil) { @connection.execute(nil) }