### Question:
BackendBase implements TraceeBackend { @Override public String getInvocationId() { return get(TraceeConstants.INVOCATION_ID_KEY); }  @Override final TraceeFilterConfiguration getConfiguration(); @Override final TraceeFilterConfiguration getConfiguration(String profileName); @Override String getInvocationId(); @Override String getSessionId();  }### Answer:
@Test public void invocationIdShortcutShouldReturnTheInvocationIdIfSet() { when(unit.get(eq(TraceeConstants.INVOCATION_ID_KEY))).thenReturn("ourInvocationId"); assertThat(unit.getInvocationId(), is("ourInvocationId")); }
@Test public void invocationIdShortcutShouldReturnNullIfNoInvocationIdIsSet() { assertThat(unit.getInvocationId(), is(nullValue())); }