### Question:
AbstractServerTracer extends AbstractTracer { protected String getClientDigestReporterRollingKey() { return null; } AbstractServerTracer(String tracerType);   }### Answer:
@Test public void getClientDigestReporterRollingKey() { String clientDigestReporterRollingKey = serverTracer.getClientDigestReporterRollingKey(); Assert.assertTrue(clientDigestReporterRollingKey == null); }