Mockito - NullpointerException when invoking method from Service

Question

Hi I am trying to test the method but it returned null and I don't know why; Method should work properly but still, I have NullPointerException

@Service
public class AzureCloudStorageService implements FileService {
    private final String connectionString;
    private final String containerName;
    private final ModelMapper modelMapper;

    public AzureCloudStorageService(@Autowired PropertyResolver propertyResolver,
        ModelMapper modelMapper) {
        this.connectionString = propertyResolver.getProperty("azure.connection.string");
        this.containerName = propertyResolver.getProperty("azure.container.name");
        this.modelMapper = modelMapper;
    }
public MultipartFile convertToMultipartImage(String image) {
        try {
            return modelMapper.map(image, MultipartFile.class);
        } catch (Exception e) {
            throw new BadRequestException(ErrorMessage.MULTIPART_FILE_BAD_REQUEST + image);
        }
    }

and the test method, maybe it`s because of final methods or something, I have no idea

@ExtendWith(SpringExtension.class)
class AzureCloudStorageServiceTest {
    @Mock
    private ModelMapper modelMapper;

    @Mock
    private AzureCloudStorageService azureCloudStorageService;

    @Test
    void convertToMultipartImage(){
        MultipartFile multipartFile = ModelUtils.getFile();
        String image = "Image";
        when(modelMapper.map(image, MultipartFile.class)).thenReturn(multipartFile);
        MultipartFile actual = azureCloudStorageService.convertToMultipartImage("Image");
            assertEquals(multipartFile,  actual);
    }
}

there is stacktrace for my program. Some exceprion and error, sorry for screens in comment but i didnt see how to edit

org.opentest4j.AssertionFailedError: 
Expected :org.springframework.mock.web.MockMultipartFile@441cc260
Actual   :null
<Click to see difference>


    at org.junit.jupiter.api.AssertionUtils.fail(AssertionUtils.java:55)
    at org.junit.jupiter.api.AssertionUtils.failNotEqual(AssertionUtils.java:62)
    at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:182)
    at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:177)
    at org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:1124)
    at greencity.service.AzureCloudStorageServiceTest.convertToMultipartImage(AzureCloudStorageServiceTest.java:46)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)

org.opentest4j.AssertionFailedError:--- Expected :org.springframework.mock.web.MockMultipartFile@441cc260 ------ Actual :null--- --------------------------- If you about this, because i dont know what is stacktrace, sorry — Feel free, Sep 21 '21 at 11:51
https://stackoverflow.com/questions/3988788/what-is-a-stack-trace-and-how-can-i-use-it-to-debug-my-application-errors — akortex, Sep 21 '21 at 11:52
https://docs.google.com/document/d/1q8nbLl2t-3Sa2NkmSO3S9lTdARkyCgOEpXxJ0s2gLPA/edit?usp=sharing link on Screenshot — Feel free, Sep 21 '21 at 11:56
Please copy and paste the stacktrace as part of you question. Do not link images moreover so from external sources. — akortex, Sep 21 '21 at 11:57

score 2 · Accepted Answer · answered Sep 21 '21 at 12:27

Your problems stems from the wrong way you do your mocks. In your code you do the following:

@Mock
private AzureCloudStorageService azureCloudStorageService;

Which effectively returns a mocked instance of AzureCloudStorageService. This is not what you want and need for this case, as this is what you need to test (i.e the unit under test). What you need to do though is to manually instantiate the AzureCloudStorageService by calling its constructor and passing in the mocked ModelMapper as well as PropertyResolver.

score 1 · Answer 2 · answered Sep 21 '21 at 12:10

1

Instead of

@Mock
private ModelMapper modelMapper;

Use into the method or in @Before method:

ModelMapper modelMapper = Mockito.mock(ModelMapper.class);

It is working for me:

ServicioCalls servicioCalls = Mockito.mock(ServicioCalls.class);
    EncapsulatedError<?> encapsulatedError = new EncapsulatedError<>(SpResult.SUCCESS_CODE, SpResult.OK, 0, null);
   Mockito.doReturn(encapsulatedError).when(servicioCalls).obtenerCalls(anyString(), anyString(), anyLong());

answered Sep 21 '21 at 12:10

Alvaro Gili

25
1
3

It doesn`t help me, because this is the same code what I did and program throws me the same exception, thank you for answer – Feel free Sep 21 '21 at 12:15

score 0 · Answer 3 · answered Sep 21 '21 at 12:49

It`s working properly and covering my method and constructor) Thank you akortex

@Test
    void convertToMultipartImage(){
        MultipartFile multipartFile = Mockito.mock(MultipartFile.class);
        AzureCloudStorageService azureCloudStorageService = new AzureCloudStorageService(propertyResolver, modelMapper);
        String image = "Image";
        when(modelMapper.map(image, MultipartFile.class)).thenReturn(multipartFile);
            assertEquals(multipartFile, azureCloudStorageService.convertToMultipartImage("Image"));
    }

score -1 · Answer 4 · answered Sep 21 '21 at 12:26

-1

Ok, try with it:

Change this:

when(modelMapper.map(image, MultipartFile.class)).thenReturn(multipartFile);

By this:

Mockito.doReturn(modelMapper).when(modelMapper).map(anyString(), any());

And set to azureCloudStorageService the mockling object modelMapper previos to call:

azureCloudStorageService.setModelMapper(modelMapper);
MultipartFile actual = azureCloudStorageService.convertToMultipartImage("Image");
assertEquals(multipartFile,  actual);

answered Sep 21 '21 at 12:26

Alvaro Gili

25
1
3

I do not think this is the correct approach. Adding a `setter` only to pass in the the mocked instance effectively denies the class of being immutable. What he needs to do is to pass in the mocked dependencies through the constructor. – akortex Sep 21 '21 at 12:28

score -1 · Answer 5 · answered Sep 21 '21 at 12:35

Ok, do you can use inheritance, creates a class dummy like it

private static class CallsRestStub extends CallsRest {

 }

When CallsRest is the original class and modelMapper protected. With it you can creates a instance of CallsRestStub instead CallSRest and sets to it the mocking object

Mockito - NullpointerException when invoking method from Service

5 Answers5