[wpinet] Handle empty txt block for mdns announcer (#4072)

wpinet/src/test/native/cpp/MulticastTest.cpp

@@ -0,0 +1,47 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <wpinet/MulticastServiceAnnouncer.h>
+#include <wpinet/MulticastServiceResolver.h>
+
+#include <thread>
+
+#include <wpi/timestamp.h>
+
+#include "gtest/gtest.h"
+
+TEST(MulticastServiceAnnouncerTest, EmptyText) {
+  const std::string_view serviceName = "TestServiceNoText";
+  const std::string_view serviceType = "_wpinotxt";
+  const int port = std::rand();
+  wpi::MulticastServiceAnnouncer announcer(serviceName, serviceType, port);
+  wpi::MulticastServiceResolver resolver(serviceType);
+
+  if (announcer.HasImplementation() && resolver.HasImplementation()) {
+    announcer.Start();
+    resolver.Start();
+
+    std::this_thread::sleep_for(std::chrono::seconds(1));
+
+    resolver.Stop();
+    announcer.Stop();
+  }
+}
+
+TEST(MulticastServiceAnnouncerTest, SingleText) {
+  const std::string_view serviceName = "TestServiceSingle";
+  const std::string_view serviceType = "_wpitxt";
+  const int port = std::rand();
+  std::array<std::pair<std::string, std::string>, 1> txt = {
+      std::make_pair("hello", "world")};
+  wpi::MulticastServiceAnnouncer announcer(serviceName, serviceType, port, txt);
+  wpi::MulticastServiceResolver resolver(serviceType);
+
+  if (announcer.HasImplementation() && resolver.HasImplementation()) {
+    announcer.Start();
+    resolver.Start();
+
+    std::this_thread::sleep_for(std::chrono::seconds(1));
+  }
+}