Mockito given().willReturn() returns sporadic result - spring

Question

I am testing a simple logic using mockito-all 1.10.19 and spring-boot-starter-parent 2.0.4.RELEASE. I have a service, which determines whether the uploaded file has the same store codes or not. If it has, IllegalArgumentException is been thrown:
public class SomeService {
private final CutoffRepository cutoffRepository;
private final Parser<Cutoff> cutoffParser;
public void saveCutoff(MultipartFile file) throws IOException {
List<Cutoff> cutoffList = cutoffParser.parse(file.getInputStream());
boolean duplicateStoreFlag = cutoffList
.stream()
.collect(Collectors
.groupingBy(Cutoff::getStoreCode, Collectors.counting()))
.values()
.stream()
.anyMatch(quantity -> quantity > 1);
if (duplicateStoreFlag) {
throw new IllegalArgumentException("There are more than one line corresponding to the same store");
}
//Some saving logic is here
}
}
I mock up cutoffParser.parse() so, that it returns ArrayList<CutOff> with two elements within it:
#RunWith(SpringRunner.class)
#SpringBootTest
public class SomeServiceTest {
#Mock
private CutoffRepository cutoffRepository;
#Mock
private Parser<Cutoff> cutoffParser;
#InjectMocks
private SomeService someService;
#Test(expected = IllegalArgumentException.class)
public void saveCutoffCurruptedTest() throws Exception {
Cutoff cutoff1 = new Cutoff();
cutoff1.setStoreCode(1);
Cutoff cutoff2 = new Cutoff();
//corruption is here: the same storeCode
cutoff2.setStoreCode(1);
List<Cutoff> cutoffList = new ArrayList<>();
cutoffList.add(cutoff1);
cutoffList.add(cutoff2);
MockMultipartFile mockMultipartFile = new MockMultipartFile("file.csv", "file".getBytes());
//here what I expect to mock up a response with the list
given(cutoffParser.parse(any())).willReturn(cutoffList);
someService.saveCutoff(mockMultipartFile);
}
}
But the behavior I encounter is sporadic. The test is passed from time to time. During debugging I sometimes get list of size 2, sometimes get list of size 0. What is the reason of such an unpredictable behavior?
I am definitely missing something. Any help is highly appreciated.
P.S. the same situation using IntelliJ Idea and Ubuntu terminal.

Answer 1

Supposedly, the reason is pointed out here https://github.com/mockito/mockito/issues/1066. #InjectMocks and #Mock<...> cause test to fail occasionally.