STY: Styling.

test/test_value.cpp

@@ -141,7 +141,7 @@ TEST(test_value, test_list) {
   auto empty_content = std::vector<int>();
   Value value_0(empty_content);
   EXPECT_TRUE(value_0.IsVector());
-  auto list_value_0 = value_0.GetAsVector();
+  auto const &list_value_0 = value_0.GetAsVector();
   EXPECT_EQ(list_value_0.size(), 0);
   EXPECT_TRUE(list_value_0.empty());
 }