JUnit with Mock Okta SDK

Seeing what I can mock with Okta SDK client.

private Client oktaClient;

Trying to create a fake application list, so I need to create fake applications.
Trying to use the Okta instantiate method.
Application app = client.instantiate(Application.class);
But app = null. Not a real object and thus can’t set the label or anything with it.

Any suggestions on how to get this working?