Add test for releasing connections back to the server

tests/test_server_connection_return.cpp

@@ -0,0 +1,96 @@
+#include "../src/ThreadPipeline.h"
+#include "config.hpp"
+#include "connection.hpp"
+#include "perfetto_categories.hpp"
+#include "server.hpp"
+#include <doctest/doctest.h>
+#include <thread>
+
+// Perfetto static storage for tests
+PERFETTO_TRACK_EVENT_STATIC_STORAGE();
+
+struct Message {
+  std::unique_ptr<Connection> conn;
+  std::string data;
+  bool done;
+};
+
+struct EchoHandler : public ConnectionHandler {
+private:
+  ThreadPipeline<Message> &pipeline;
+
+public:
+  explicit EchoHandler(ThreadPipeline<Message> &pipeline)
+      : pipeline(pipeline) {}
+
+  void on_data_arrived(std::string_view data,
+                       std::unique_ptr<Connection> &conn_ptr) override {
+    assert(conn_ptr);
+    auto guard = pipeline.push(1, true);
+    for (auto &message : guard.batch) {
+      message.conn = std::move(conn_ptr);
+      message.data = data;
+      message.done = false;
+    }
+  }
+};
+
+TEST_CASE("Echo server with connection ownership transfer") {
+  weaseldb::Config config;
+  config.server.io_threads = 1;
+  config.server.epoll_instances = 1;
+
+  ThreadPipeline<Message> pipeline{10, {1}};
+  EchoHandler handler{pipeline};
+  auto echoThread = std::thread{[&]() {
+    for (;;) {
+      auto guard = pipeline.acquire(0, 0);
+      for (auto &message : guard.batch) {
+        bool done = message.done;
+        if (done) {
+          return;
+        }
+        assert(message.conn);
+        message.conn->appendMessage(message.data);
+        Server::releaseBackToServer(std::move(message.conn));
+      }
+    }
+  }};
+
+  // Create server with NO listen sockets (empty vector)
+  auto server = Server::create(config, handler, {});
+
+  std::thread server_thread([&server]() { server->run(); });
+
+  // Create local connection
+  int client_fd = server->createLocalConnection();
+  REQUIRE(client_fd > 0);
+
+  // Write some test data
+  const char *test_message = "Hello, World!";
+  ssize_t bytes_written = write(client_fd, test_message, strlen(test_message));
+  REQUIRE(bytes_written == strlen(test_message));
+
+  // Read the echoed response
+  char buffer[1024] = {0};
+  ssize_t bytes_read = read(client_fd, buffer, sizeof(buffer) - 1);
+  if (bytes_read == -1) {
+    perror("read failed");
+  }
+  REQUIRE(bytes_read == strlen(test_message));
+
+  // Verify we got back exactly what we sent
+  CHECK(std::string(buffer, bytes_read) == std::string(test_message));
+
+  // Cleanup
+  close(client_fd);
+  server->shutdown();
+  server_thread.join();
+  {
+    auto guard = pipeline.push(1, true);
+    for (auto &message : guard.batch) {
+      message.done = true;
+    }
+  }
+  echoThread.join();
+}