@Override
    public void createOrUpdateDeviceKey(DeviceKey deviceKey) {

        // Add the device key to the store, if the device key already exists
        // then it will be replaced with the new one.
        deviceKeys.put(deviceKey.deviceKeyId(), deviceKey);
    }
@Test(expected = NullPointerException.class)
    public void testAddNullKey() {
        deviceKeyStore.createOrUpdateDeviceKey(null);
    }