add test

unit_tests/util/json_render.cpp

@@ -0,0 +1,23 @@
+#include "util/json_container.hpp"
+#include "util/json_renderer.hpp"
+
+#include <boost/test/unit_test.hpp>
+
+#include <iostream>
+
+BOOST_AUTO_TEST_SUITE(json_renderer)
+
+using namespace osrm;
+using namespace osrm::util;
+
+BOOST_AUTO_TEST_CASE(number_truncating)
+{
+    std::string str;
+    json::Renderer<std::string> renderer(str);
+
+    // this number would have more than 10 decimals if not truncated
+    renderer(json::Number{42.9995999594999399299});
+    BOOST_CHECK_EQUAL(str, "42.999599959");
+}
+
+BOOST_AUTO_TEST_SUITE_END()