### Question:
CExFirstOracle implements BlackBoxOracle<A, I, D> { @Override public @Nullable DefaultQuery<I, D> findCounterExample(A hypothesis, Collection<? extends I> inputs) { for (PropertyOracle<I, ? super A, ?, D> propertyOracle : propertyOracles) { final DefaultQuery<I, D> result = propertyOracle.findCounterExample(hypothesis, inputs); if (result != null) { assert isCounterExample(hypothesis, result.getInput(), result.getOutput()); return result; } } return null; } CExFirstOracle();  CExFirstOracle(PropertyOracle<I, A, ?, D> propertyOracle);  CExFirstOracle(Collection<? extends PropertyOracle<I, ? super A, ?, D>> propertyOracles); @Override List<PropertyOracle<I, ? super A, ?, D>> getPropertyOracles(); @Override @Nullable DefaultQuery<I, D> findCounterExample(A hypothesis, Collection<? extends I> inputs);  }### Answer:
@Test public void testFindCounterExample() { final DefaultQuery<Boolean, Boolean> ce = oracle.findCounterExample(automaton, inputs); Assert.assertEquals(ce, query); Mockito.verify(po1).disprove(automaton, inputs); Mockito.verify(po2, Mockito.never()).disprove(automaton, inputs); Mockito.verify(po2, Mockito.never()).findCounterExample(automaton, inputs); }