assertEquals(1, client.getActiveRegistrationCount());

        // Unregister
        client.unregister(registration).get(5, TimeUnit.SECONDS);

        assertEquals(0, client.getActiveRegistrationCount());

        verify(mockRpc).register(any(WitnessRegisterRequest.class));

        return witnessServer;
    }

    /**
     * Gets the number of active registrations.
     *
     * @return the number of active registrations
     */
    public int getActiveRegistrationCount() {
        return registrations.size();
    }

    @Override
    public void close() {
        // Stop all async notification tasks first