### Question:
DistrictTeamExtractor implements Func1<List<DistrictRanking>, DistrictRanking> { @Override public DistrictRanking call(List<DistrictRanking> districtTeams) { for (int i = 0; i < districtTeams.size(); i++) { DistrictRanking districtTeam = districtTeams.get(i); if (districtTeam.getTeamKey().equals(mTeamKey)) { return districtTeam; } } return null; } DistrictTeamExtractor(String teamKey); @Override DistrictRanking call(List<DistrictRanking> districtTeams);  }### Answer:
@Test public void testDistrictTeamExtractorNotFound() { mExtractor = new DistrictTeamExtractor(mNotFoundTeamKey); DistrictRanking extracted = mExtractor.call(mDistrictTeams); assertNull(extracted); }