diff --git a/cmake/build.cmake b/cmake/build.cmake
index 91aae76a..0b5b9cec 100644
--- a/cmake/build.cmake
+++ b/cmake/build.cmake
@@ -21,7 +21,7 @@ endif()
 if (MSVC)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /std:c++latest")
 else ()
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}  -pthread -std=c++20")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -pthread -std=c++20")
 endif ()
 
 # --------------------- Gcc
diff --git a/include/cinatra/coro_http_response.hpp b/include/cinatra/coro_http_response.hpp
index c0ea40e6..eb720765 100644
--- a/include/cinatra/coro_http_response.hpp
+++ b/include/cinatra/coro_http_response.hpp
@@ -144,8 +144,6 @@ class coro_http_response {
   void clear() {
     head_.clear();
     content_.clear();
-    head_.shrink_to_fit();
-    content_.shrink_to_fit();
 
     resp_headers_.clear();
     resp_headers_sv_.clear();
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 0739a42d..4689b335 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -27,7 +27,7 @@ if(ENABLE_FILE_IO_URING)
 endif()
 
 if (UNIX)
-SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pthread")
+SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -pthread")
 endif()
 
 ## manual import
diff --git a/tests/test_coro_http_server.cpp b/tests/test_coro_http_server.cpp
index 9b2fb437..ac7ee48d 100644
--- a/tests/test_coro_http_server.cpp
+++ b/tests/test_coro_http_server.cpp
@@ -30,12 +30,11 @@ using namespace std::chrono_literals;
 
 TEST_CASE("coro_server example, will block") {
   return;  // remove this line when you run the coro server.
-  cinatra::coro_http_server server(1, 9001);
+  cinatra::coro_http_server server(std::thread::hardware_concurrency(), 9001);
   server.set_http_handler<cinatra::GET, cinatra::POST>(
       "/", [](coro_http_request &req, coro_http_response &resp) {
         // response in io thread.
-        std::cout << std::this_thread::get_id() << "\n";
-        resp.set_keepalive(true);
+        std::this_thread::sleep_for(10ms);
         resp.set_status_and_content(cinatra::status_type::ok, "hello world");
       });
 
@@ -43,17 +42,19 @@ TEST_CASE("coro_server example, will block") {
       "/coro",
       [](coro_http_request &req,
          coro_http_response &resp) -> async_simple::coro::Lazy<void> {
-        std::cout << std::this_thread::get_id() << "\n";
-
-        co_await coro_io::post([&] {
+        co_await coro_io::post([&]() {
           // coroutine in other thread.
-          std::cout << std::this_thread::get_id() << "\n";
-          resp.set_status(cinatra::status_type::ok);
-          resp.set_content("hello world in coro");
+          std::this_thread::sleep_for(10ms);
+          resp.set_status_and_content(cinatra::status_type::ok, "hello world");
         });
-        std::cout << std::this_thread::get_id() << "\n";
         co_return;
       });
+
+  server.set_http_handler<cinatra::GET, cinatra::POST>(
+      "/echo", [](coro_http_request &req, coro_http_response &resp) {
+        // response in io thread.
+        resp.set_status_and_content(cinatra::status_type::ok, "hello world");
+      });
   server.sync_start();
   CHECK(server.port() > 0);
 }