### Question:
SystemCredentials extends Credentials { public SystemCredentials(String instanceID, String principal, AuthenticationToken token) { super(principal, token); AS_THRIFT = super.toThrift(instanceID); } SystemCredentials(String instanceID, String principal, AuthenticationToken token); static SystemCredentials get(String instanceID, SiteConfiguration siteConfig); @Override TCredentials toThrift(String instanceID);  }### Answer:
@Test public void testSystemCredentials() { Credentials a = SystemCredentials.get(instanceId, siteConfig); Credentials b = SystemCredentials.get(instanceId, siteConfig); assertEquals(a, b); }