public void delete(final String key) {
        client.getKVClient().delete(ByteSequence.from(key, StandardCharsets.UTF_8));
    }
@Test
    public void delete() {
        CompletableFuture<DeleteResponse> delete = mock(CompletableFuture.class);
        when(client.getKVClient().delete(ByteSequence.from(TEST_KEY, StandardCharsets.UTF_8))).thenReturn(delete);
        etcdClient.delete(TEST_KEY);
        verify(client.getKVClient(), times(1)).delete(any(ByteSequence.class));
    }