### Question:
MmdTool extends BasicTool { static Observation findObservation(String sensorName, Matchup matchup, PersistenceManager persistenceManager) { final ReferenceObservation referenceObservation = matchup.getRefObs(); if (sensorName.equals(referenceObservation.getSensor())) { return referenceObservation; } for (final Coincidence coincidence : matchup.getCoincidences()) { final Observation observation = coincidence.getObservation(); if (sensorName.equals(observation.getSensor())) { return observation; } else { persistenceManager.detach(observation); persistenceManager.detach(coincidence); } } return null; } MmdTool(); static void main(String[] args); @Override void initialize();  }### Answer:
@Test public void testFindObservation_nonePresent() { final Matchup matchup = createMatchupWithRefObs("different"); matchup.setCoincidences(new ArrayList<Coincidence>()); final Observation observation = MmdTool.findObservation("dont_care", matchup, null); assertNull(observation); }
@Test public void testFindObservation_referenceObservation() { final Matchup matchup = createMatchupWithRefObs("the_one"); final Observation observation = MmdTool.findObservation("the_one", matchup, null); assertNotNull(observation); }
@Test public void testFindObservation_fromCoincidences() { final Matchup matchup = createMatchupWithRefObs("different"); addCoincidence(matchup, "the_one"); final Observation result = MmdTool.findObservation("the_one", matchup, null); assertNotNull(result); }
@Test public void testFindObservation_notInCoincidences_detaches() { final Matchup matchup = createMatchupWithRefObs("different"); final List<Coincidence> coincidences = new ArrayList<>(); final Observation observation = new Observation(); observation.setSensor("also_different"); final Coincidence coincidence = new Coincidence(); coincidence.setObservation(observation); coincidences.add(coincidence); matchup.setCoincidences(coincidences); final PersistenceManager persistenceManager = mock(PersistenceManager.class); final Observation result = MmdTool.findObservation("the_one", matchup, persistenceManager); assertNull(result); verify(persistenceManager, times(1)).detach(observation); verify(persistenceManager, times(1)).detach(coincidence); verifyNoMoreInteractions(persistenceManager); }