Add move-only handler tests

test/beast/websocket/write.cpp

@@ -631,6 +631,16 @@ public:
         asio_handler_is_continuation(&op);
     }
 
+    void
+    testMoveOnly()
+    {
+        boost::asio::io_context ioc;
+        stream<test::stream> ws{ioc};
+        ws.async_write_some(
+            true, boost::asio::const_buffer{},
+            move_only_handler{});
+    }
+
     void
     run() override
     {
@@ -639,6 +649,7 @@ public:
         testAsyncWriteFrame();
         testIssue300();
         testContHook();
+        testMoveOnly();
     }
 };