Passing System properties into a void method in jUnit

I'm trying to unit test some code utilizing Hazelcast. Most of the code is straightforward, but I've been having hangups with the class constructor.

public ClientViewer() {
    setup();
}

private void setup() {
    ClientConfig clientConfig = new ClientConfig();
    clientConfig.getGroupConfig.setName(System.getProperty("hazelcast.group")).setPassword(System.getProperty("hazelcast.password"));
    clientConfig.getNetworkConfig().addAddress(System.getProperty("hazelcast.url"));
    client= HazelcastClient.newHazelcastClient(clientConfig);
}

So any time I try to create a test object to call/test its methods, it keeps throwing an IllegalArgumentException. So I decided to set each property individually before creating the test object using test data.

TEST_GROUP = "testGroup";
TEST_PASSWORD = "testPassword";
TEST_URL = "testUrl";

System.setProperty("hazelcast.group", TEST_GROUP);
System.setProperty("hazelcast.password", TEST_PASSWORD);
System.setProperty("hazelcast.url", TEST_URL);

But now I'm getting an InvocationTargetException. What am I missing? Is there a way to fool the setup method without dependency injection?

(BTW: I'm aware dependency injection is kind of an obvious good practice, but that idea is somewhat lost among my peers. Suffice to say, that's not an option in this scenario.)