### Question:
Client { public void checkNotNull() { if (dataSubjectId == null || dataControllerId == null || appId == null) throw new NullPointerException("Parameters which describe" + " a client cannot be null"); } Client(final String dataSubjectId, final String dataControllerId,
            final String appId); void checkNotNull(); String getDataSubjectId(); String getDataControllerId(); String getAppId();  }### Answer:
@Test(expected = NullPointerException.class) public void testCheckNotNull() { Client client = new Client("1", "1", "1"); client.checkNotNull(); client = new Client("1", "1", null); client.checkNotNull(); }