Don't count_down past 0

tests/test_server.cpp

@@ -3,22 +3,36 @@
 #include "connection_handler.hpp"
 #include "server.hpp"
 
+#include <atomic>
 #include <doctest/doctest.h>
 #include <latch>
 #include <string_view>
 #include <thread>
 
+struct Event {
+  void wait() { done_.wait(); }
+  void set() {
+    if (!set_.exchange(true, std::memory_order_relaxed)) {
+      done_.count_down();
+    }
+  }
+
+private:
+  std::latch done_{1};
+  std::atomic<bool> set_;
+};
+
 struct EchoHandler : ConnectionHandler {
   Arena arena;
   std::span<std::string_view> reply;
   WeakRef<MessageSender> wconn;
-  std::latch done{1};
+  Event done;
   void on_data_arrived(std::string_view data, Connection &conn) override {
     reply = arena.allocate_span<std::string_view>(1);
     reply[0] = arena.copy_string(data);
     wconn = conn.get_weak_ref();
     CHECK(wconn.lock());
-    done.count_down();
+    done.set();
   }
 };
 
@@ -60,8 +74,8 @@ struct ShutdownTestHandler : ConnectionHandler {
   Arena arena;
   std::span<std::string_view> reply;
   WeakRef<MessageSender> wconn;
-  std::latch received_data{1};
-  std::latch connection_closed_latch{1};
+  Event received_data;
+  Event connection_closed_latch;
   ConnectionShutdown shutdown_mode = ConnectionShutdown::None;
   std::atomic<bool> connection_closed{false};
 
@@ -69,12 +83,12 @@ struct ShutdownTestHandler : ConnectionHandler {
     reply = arena.allocate_span<std::string_view>(1);
     reply[0] = arena.copy_string(data);
     wconn = conn.get_weak_ref();
-    received_data.count_down();
+    received_data.set();
   }
 
   void on_connection_closed(Connection &) override {
     connection_closed = true;
-    connection_closed_latch.count_down();
+    connection_closed_latch.set();
   }
 };