NPE when using mock Kubernetes Server

[lalithsuresh]

Following what I could find in kubernetes-tests, I'm running into the following NPE when using the Kubernetes mock server.

public class MyTest {
    @Rule
    public KubernetesServer server = new KubernetesServer(false);

    @Test
    public void testInformer() {
        System.out.println(server.expect());
    }
}

NPE:

java.lang.NullPointerException
	at io.fabric8.kubernetes.client.server.mock.KubernetesServer.expect(KubernetesServer.java:72)

The dependencies I used were:

         <dependency>
            <groupId>io.fabric8</groupId>
            <artifactId>kubernetes-client</artifactId>
            <version>4.6.1</version>
        </dependency>
        <dependency>
            <groupId>io.fabric8</groupId>
            <artifactId>kubernetes-server-mock</artifactId>
            <version>4.6.1</version>
            <scope>test</scope>
        </dependency>   

I've tried different variants of the KubernetesServer constructors to no avail. What am I missing?