anchor.diff:      });
   
       testWithoutContext('Prints helpful message when there is no ipv4 link local address.', () async {
  -      final MDnsClient client = getMockClient(<PtrResourceRecord>[], <String, List<SrvResourceRecord>>{});
  +      final MDnsClient client = FakeMDnsClient(<PtrResourceRecord>[], <String, List<SrvResourceRecord>>{});
         final BufferLogger logger = BufferLogger.test();
         final MDnsObservatoryDiscovery portDiscovery = MDnsObservatoryDiscovery(
           mdnsClient: client,
  
positive.code:     });
  
      testWithoutContext('Throws Exception when client throws OSError on start', () async {
        final MDnsClient client = MockMDnsClient();
        when(client.start()).thenAnswer((_) {
          throw const OSError('Operation not suppoted on socket', 102);
        });
  
        final MDnsObservatoryDiscovery portDiscovery = MDnsObservatoryDiscovery(
          mdnsClient: client,
  
negative.code:     });
  
      testWithoutContext('Query returns null', () async {
        final MDnsClient client = FakeMDnsClient(
          <PtrResourceRecord>[],
           <String, List<SrvResourceRecord>>{},
        );
  