@Override
    public Map<String, String> discoverLocalMetadata() {
        if (memberMetadata.isEmpty()) {
            memberMetadata.put(PartitionGroupMetaData.PARTITION_GROUP_ZONE, gcpClient.getAvailabilityZone());
        }
        return memberMetadata;
    }
@Test
    public void discoverLocalMetadata() {
        // given
        given(gcpClient.getAvailabilityZone()).willReturn(ZONE);

        // when
        Map<String, String> result1 = gcpDiscoveryStrategy.discoverLocalMetadata();
        Map<String, String> result2 = gcpDiscoveryStrategy.discoverLocalMetadata();

        // then
        assertEquals(ZONE, result1.get(PartitionGroupMetaData.PARTITION_GROUP_ZONE));
        assertEquals(ZONE, result2.get(PartitionGroupMetaData.PARTITION_GROUP_ZONE));
        verify(gcpClient).getAvailabilityZone();
    }