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How to test update function in Rest API?

I can't find a way to test my update method using JUnit. I am mocking the necessary repo and services. But when I call findById(Mockito.any()) it can't find anything so it throws an exception.
Here is my test class:
#ExtendWith(MockitoExtension.class)
class ApplicantServiceTest {
#Mock
private ApplicantRepository applicantRepository;
#Mock
private CreditRatingService creditRatingService;
#Mock
private ApplicantMapper applicantMapper;
#InjectMocks
private ApplicantService applicantService;
#Test
void update() {
Applicant applicant = getSampleApplicants().get(1);
Applicant updatedApplicant = new Applicant(1L,2141245L,"ege","c0skun",2523,"21412412",null,null);
Mockito.when(applicantService.update(applicantMapper.toDTO(applicant),Mockito.any())).thenReturn(applicant);
Assert.assertEquals(applicant.getIdentificationNumber(),updatedApplicant.getIdentificationNumber());
Assert.assertEquals(applicant.getPhoneNumber(), updatedApplicant.getPhoneNumber());
Assert.assertEquals(applicant.getFirstName(), updatedApplicant.getFirstName());
assertEquals(applicant.getMonthlyIncome(), updatedApplicant.getMonthlyIncome());
Assert.assertEquals(applicant.getId(), updatedApplicant.getId());
}
And this is the method I am trying to test:
public Applicant update(ApplicantDTO applicantDTO,Long id) {
Applicant byId = getById(id);
if (applicantDTO.getMonthlyIncome()!=byId.getMonthlyIncome()){
byId.setMonthlyIncome(applicantDTO.getMonthlyIncome());
}
if (!Objects.equals(applicantDTO.getFirstName(), byId.getFirstName())){
byId.setFirstName(applicantDTO.getFirstName());
}
if (!Objects.equals(applicantDTO.getLastName(), byId.getLastName())){
byId.setLastName(applicantDTO.getLastName());
}
if (!Objects.equals(applicantDTO.getPhoneNumber(), byId.getPhoneNumber())){
byId.setPhoneNumber(applicantDTO.getPhoneNumber());
}
if (!Objects.equals(applicantDTO.getIdentificationNumber(), byId.getIdentificationNumber())){
byId.setIdentificationNumber(applicantDTO.getIdentificationNumber());
}
return applicantRepository.save(byId);
}
This is the output:
17:43:19.520 [main] ERROR com.egecoskun.finalproject.services.ApplicantService - Applicant not found by id : null
Related Applicant not found with : [id : null]
EntityNotFoundException(details=Some Special Details)
at com.egecoskun.finalproject.services.ApplicantService.lambda$getById$0(ApplicantService.java:47)
at java.base/java.util.Optional.orElseThrow(Optional.java:403)
at com.egecoskun.finalproject.services.ApplicantService.getById(ApplicantService.java:45)
at com.egecoskun.finalproject.services.ApplicantService.update(ApplicantService.java:75)
at com.egecoskun.finalproject.services.ApplicantServiceTest.update(ApplicantServiceTest.java:136)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
...
Can someone explain how to unit test my update method?

The problem with your test code is that you've mixed mocking a method for a mock object (e.g. applicantRepository) with calling the tested method on an object under test (applicantService). We use when(...) to define the mocked behavior in Mockito and after that the actually tested code should be called (without the when()).
What you probably want to do is: mock retrieving the applicant object by ID, mock saving the modified object, run the update method to test it and assert the result.
To mock the behavior of the applicantRepository you need to tell Mockito what is the expected outcome of its methods calls, for example (I made a few assumptions for the code that is not attached):
when(applicantRepository.findById(anyLong())).thenReturn(applicantFromDb);
when(applicantRepository.save(notNull())).thenAnswer(returnsFirstArg());
(applicantFromDb is an object created in the test method)
After that when you call your update method, the mocked behavior above will be used:
Applicant result = applicantService.update(...);
Now you can assert the result returned from the tested method.

ApplicationService is your class under test. The exception you're getting is coming from ApplicationService.getById() method called at the start of update() method you're testing. You did not show us that method, but at a guess it calls the repository to get an instance by id. Your Repository mock is not set up to return anything when asked for any entity, so it returns null. Which seems to trigger the orElseThrow clause in the getById() method.
As such what you're seeing is likely the expected behaviour - when trying to update with an id that does not exist in the repository (repository returns null) service throws an exception. If you want to test the case where the entity is present you need to mock the repository appropriately.

Sometimes we get error: "Previous MockitoSession was not concluded with 'finishMocking()'" [duplicate]

I am getting following exception while running the tests. I am using Mockito for mocking. The hints mentioned by Mockito library are not helping.
org.mockito.exceptions.misusing.UnfinishedStubbingException:
Unfinished stubbing detected here:
-> at com.a.b.DomainTestFactory.myTest(DomainTestFactory.java:355)
E.g. thenReturn() may be missing.
Examples of correct stubbing:
when(mock.isOk()).thenReturn(true);
when(mock.isOk()).thenThrow(exception);
doThrow(exception).when(mock).someVoidMethod();
Hints:
1. missing thenReturn()
2. you are trying to stub a final method, you naughty developer!
at a.b.DomainTestFactory.myTest(DomainTestFactory.java:276)
..........
Test Code from DomainTestFactory. When I run the following test, I see the exception.
#Test
public myTest(){
MyMainModel mainModel = Mockito.mock(MyMainModel.class);
Mockito.when(mainModel.getList()).thenReturn(getSomeList()); // Line 355
}
private List<SomeModel> getSomeList() {
SomeModel model = Mockito.mock(SomeModel.class);
Mockito.when(model.getName()).thenReturn("SomeName"); // Line 276
Mockito.when(model.getAddress()).thenReturn("Address");
return Arrays.asList(model);
}
public class SomeModel extends SomeInputModel{
protected String address;
protected List<SomeClass> properties;
public SomeModel() {
this.Properties = new java.util.ArrayList<SomeClass>();
}
public String getAddress() {
return this.address;
}
}
public class SomeInputModel{
public NetworkInputModel() {
this.Properties = new java.util.ArrayList<SomeClass>();
}
protected String Name;
protected List<SomeClass> properties;
public String getName() {
return this.Name;
}
public void setName(String value) {
this.Name = value;
}
}

You're nesting mocking inside of mocking. You're calling getSomeList(), which does some mocking, before you've finished the mocking for MyMainModel. Mockito doesn't like it when you do this.
Replace
#Test
public myTest(){
MyMainModel mainModel = Mockito.mock(MyMainModel.class);
Mockito.when(mainModel.getList()).thenReturn(getSomeList()); --> Line 355
}
with
#Test
public myTest(){
MyMainModel mainModel = Mockito.mock(MyMainModel.class);
List<SomeModel> someModelList = getSomeList();
Mockito.when(mainModel.getList()).thenReturn(someModelList);
}
To understand why this causes a problem, you need to know a little about how Mockito works, and also be aware in what order expressions and statements are evaluated in Java.
Mockito can't read your source code, so in order to figure out what you are asking it to do, it relies a lot on static state. When you call a method on a mock object, Mockito records the details of the call in an internal list of invocations. The when method reads the last of these invocations off the list and records this invocation in the OngoingStubbing object it returns.
The line
Mockito.when(mainModel.getList()).thenReturn(someModelList);
causes the following interactions with Mockito:
Mock method mainModel.getList() is called,
Static method when is called,
Method thenReturn is called on the OngoingStubbing object returned by the when method.
The thenReturn method can then instruct the mock it received via the OngoingStubbing method to handle any suitable call to the getList method to return someModelList.
In fact, as Mockito can't see your code, you can also write your mocking as follows:
mainModel.getList();
Mockito.when((List<SomeModel>)null).thenReturn(someModelList);
This style is somewhat less clear to read, especially since in this case the null has to be casted, but it generates the same sequence of interactions with Mockito and will achieve the same result as the line above.
However, the line
Mockito.when(mainModel.getList()).thenReturn(getSomeList());
causes the following interactions with Mockito:
Mock method mainModel.getList() is called,
Static method when is called,
A new mock of SomeModel is created (inside getSomeList()),
Mock method model.getName() is called,
At this point Mockito gets confused. It thought you were mocking mainModel.getList(), but now you're telling it you want to mock the model.getName() method. To Mockito, it looks like you're doing the following:
when(mainModel.getList());
// ...
when(model.getName()).thenReturn(...);
This looks silly to Mockito as it can't be sure what you're doing with mainModel.getList().
Note that we did not get to the thenReturn method call, as the JVM needs to evaluate the parameters to this method before it can call the method. In this case, this means calling the getSomeList() method.
Generally it is a bad design decision to rely on static state, as Mockito does, because it can lead to cases where the Principle of Least Astonishment is violated. However, Mockito's design does make for clear and expressive mocking, even if it leads to astonishment sometimes.
Finally, recent versions of Mockito add an extra line to the error message above. This extra line indicates you may be in the same situation as this question:
3: you are stubbing the behaviour of another mock inside before 'thenReturn' instruction if completed

For those who use com.nhaarman.mockitokotlin2.mock {}
Workaround 1
This error occurs when, for example, we create a mock inside another mock
mock {
on { x() } doReturn mock {
on { y() } doReturn z()
}
}
The solution to this is to create the child mock in a variable and use the variable in the scope of the parent mock to prevent the mock creation from being explicitly nested.
val liveDataMock = mock {
on { y() } doReturn z()
}
mock {
on { x() } doReturn liveDataMock
}
Workaround 2
Make sure all your mocks that should have a thenReturn.
GL

org.mockito.exceptions.misusing.UnfinishedStubbingException:
Unfinished stubbing detected here:
E.g. thenReturn() may be missing.
For mocking of void methods try out below:
//Kotlin Syntax
Mockito.`when`(voidMethodCall())
.then {
Unit //Do Nothing
}

AbcService abcService = mock(AbcService.class);
Check the syntax:
doThrow(new RunTimeException()).when(abcService).add(any(), any())
Common Mistake as seen below:
A. doThrow(new RunTimeException()).when(abcService.add(any(), any()))
Similarly, check for when().thenReturn(), so on.

I am so exited with detailed answer of #Luke Woodward that want to share a workaround.
As #Luke Woodward explained, we can not have two calls like
when(mainModel.getList());
// ...
when(model.getName()).thenReturn(...);
Than can occurs in call chain.
But in case you will use construction:
doReturn(mockToken("token3")).when(mock).getAccessToken();
when
OAuth2AccessToken mockToken(String tokenVal){
OAuth2AccessToken token = Mockito.mock(OAuth2AccessToken.class);
doReturn( 60 ).when(token).getExpiresIn();
doReturn(tokenVal).when(token).getValue();
return token;
}
all will works as expected.

Spring boot mocked object returning null on call

I am using #RunWith(SpringRunner.class) to writing unit test case to mock the object. I am trying to mock the repository instance which is accepting request object and returning response, but in unit test case implementation I have mocked the repository using #MockBean annotation and register the it's method call using Mockito.when(respository.post(request)).thenReturn(response). But this call is returning null.

I faced similar situation, the problem is given parameter in Mockito.when() block may not be the same as spring generated. I'll explain my case below, hope to help you:
Product product = new Product(..);
Mockito.when(service.addProduct(product)).thenReturn(saveProduct)
When I send a request, spring generates new Project object which has same fields with product but instance is different. That is, Mockito cannot catch when statement. I changed it like below and it's worked:
Mockito.when(service.addProduct(Mockito.any())).thenReturn(savedProduct)

I figured it out. But the solution is still weird to me...
I was facing this issue because, I was instantiating the request and response in #Before annotated method... as describing below.
#Before
public void setup() {
Request reqA = new Request();
reqA.set..(..);
Response res = new Response();
res.set..(..);
Mockito.when(this.respository.post(reqA)).thenReturn(res);
}
#Test
public void test() {
// Creating Request instance again with all same properties.
// Such that this req instance is technically similarly as instantiated in #Before annotated method (above).
// By, implementing the equals and hashCode method.
Request reqB = new Request();
reqB.set..(..);
// Getting res as 'null' here....
Response res = this.service.post(reqB);
}
Since, reqA and reqB are technically similar then why mocked call not returning the same response as registered.
If I moved setup() method code inside test() method every thing starts working !!!!!

I had the same issue here, vsk.rahul's comment helped me a lot.
I was trying to to use a method to return a mock interaction, but not succeeded, turning it into a static method gave me the expected behavior.
Problem:
The method bar.foo() was returning null for any interaction
public void test1() {
doReturn(mockReturn()).when(bar).foo();
}
private String mockReturn() {
return "abc";
}
Solution:
The method bar.foo() is returning abc String for any interaction
public void test1() {
doReturn(mockReturn()).when(bar).foo();
}
private static String mockReturn() {
return "abc";
}

How to get result from not mocked method?

I have a problem with getting result from method which is not mocked. I dont want to mock the result but to achieve the real result from this method. The method works in application, so this is not the problem. I have a test:
#Test
public void shouldGetCompaniesToSelect() throws Exception {
Company company = new Company("company", new Address());
Company relatedCompany1 = new Company("relatedCompanyName1", new Address());
Company notRelatedCompany = new Company("notRelatedCompanyName", new Address());
Company relatedCompany2 = new Company("relatedCompanyName2", new Address());
CompanyRelation companyRelation1 = new CompanyRelation(relatedCompany1);
CompanyRelation companyRelation2 = new CompanyRelation(relatedCompany2);
company.getCompanyRelations().add(companyRelation1);
company.getCompanyRelations().add(companyRelation2);
when(companyServiceMock.findAll()).thenReturn(Arrays.asList
(company, relatedCompany1, notRelatedCompany, relatedCompany2));
when(companyServiceMock.findOne(1L)).thenReturn(company);
List<Company> companiesToSelect = companyServiceMock.findCompaniesToSelect(company);
mockMvc.perform(get("/company/1"))
.andExpect(model().attribute("companiesToSelect", hasSize(1)))
.andExpect(model().attribute("companiesToSelect", hasItem(
hasProperty("relatedCompany", hasProperty(
"name", is("notRelatedCompanyName")
)))));
}
There are 2 mocked methods (findAll and findOne) and then I want to execute method and get real results from findCompaniesToSelect(company - this is object created to test). Size of the companiesToSelect should be 1, but it returns 0.
findCompaniesToSelect method:
public List<Company> findCompaniesToSelect(Company company) {
List<Company> companiesToSelect = companyRepository.findAll();
for (CompanyRelation companyRelation :
company.getCompanyRelations()) {
companiesToSelect.remove(companyRelation.getRelatedCompany());
}
companiesToSelect.remove(company);
return companiesToSelect;
}
How can I do that?
EDIT 1:
Okay, so I've changed it into #Spy and changed stubs into:
Mockito.doReturn(Arrays.asList(company, relatedCompany1,
notRelatedCompany, relatedCompany2)).when(companyServiceMock).findAll();
Mockito.doReturn(company).when(companyServiceMock).findOne(1L);
But when I run the test, the findCompaniesToSelect() method is using real companies instead of mocked companies.
Okay, so now the problem is when the findCompaniesToSelect() method is called, the companyRepository.findAll method is called. I want to call mocked findAll method from test to get mocked companies instead of real companies.
EDIT 2:
Okay, the problem was because findCompaniesToSelect() method uses repository, not a service. :D

If you want to have a combination of mocked methods and real method calls on an object then you need to use a spy instead of a mock.
#Spy
CompanyService companyServiceSpy
You will need to stub your mock methods differently though. using doReturn(...).when(...) instead of the stubbing you are currently using.
Have a look at http://www.baeldung.com/mockito-spy for more information on using spies.
EDIT: Since you are mocking some behaviour in your test you should use a standalone set up for your MockMvc object and inject the mock into your controller like so:
MockMvc mockMvc;
#Spy
CompanyService companyServiceSpy;
#InjectMocks
CompanyController companyController;
#Before
public void setup() {
MockitoAnnotations.initMocks(this);
mockMvc = MockMvcBuilders.standaloneSetup(companyController).build();
}
EDIT 2: You may also be able to resolve this just by changing #Spy to #SpyBean in your current set up. Not 100% sure on this because i'm not fully familiar with how Spring boot sets up tests.

This is happening because your service class i.e. companyService is mocked.
I should suggested to use Restassured for testing your Restservice, where it didn't require to create mock for different methods of your RestService components i.e. you don't need to mock CompanyService.
For further reading:
RestAssured
Example Code for RestAssured testing

Calling method on real object instead calling on Mock object

I faced next issue when I have been writing Junit tests with using Mockito. My test invokes methods on real object instead mock object and I receive NullPointerException. Here is my code:
public class JSFUtilsTest {
public JSFUtilsTest() { }
JSFUtils jsfUtils = mock(JSFUtils.class);
FacesContext facesContext = ContextMocker.mockFacesContext();
ExternalContext extContext = mock(ExternalContext.class);
Application app = mock(Application.class);
ExpressionFactory exFactory = mock(ExpressionFactory.class);
ELContext elContext = mock(ELContext.class);
ValueExpression valExp = mock(ValueExpression.class);
#Test
public void testResolveExpression() {
when(jsfUtils.resolveExpression("expression")).thenAnswer(new Answer<Object>(){
public Object answer(InvocationOnMock invocation){
when(facesContext.getApplication()).thenReturn(app);
when(app.getExpressionFactory()).thenReturn(exFactory);
when(facesContext.getELContext()).thenReturn(elContext);
when(exFactory.createValueExpression(elContext, "expression", Object.class)).thenReturn(valExp);
when(valExp.getValue(elContext)).thenReturn(anyObject());
return valExp.getValue(elContext);
}
});
jsfUtils.resolveExpression(anyString());
verify(jsfUtils).resolveExpression(anyString());
assertNotNull(jsfUtils.resolveExpression(anyString()));
}
}
Instead calling resolveExpression() on Mock, I have got calling on JSFUtils object. JSFUtils.java and JSFUtilsTest.java are located in different packages. Can anybody help me? Thanks in advance!

I assume that this is just an example and in real test you do not call methods on the mock directly, but inject the dependencies to OUT.
You are expecting your mock to answer when you are calling jsfUtils.resolveExpression("expression"). In fact you are not calling it. I would suggest to change it to jsfUtils.resolveExpression(anyString()) and if you need it to be called with some specific string, you can check it the verify block: verify(jsfUtils).resolveExpression("expression");
Also calling jsfUtils.resolveExpression(anyString()); is not the right approach. Method anyString() is designed for stubbing not for real call.

Instead calling resolveExpression() on Mock, I have got calling on JSFUtils object.
Then do not create a mock, but a spy:
//JSFUtils jsfUtils = mock(JSFUtils.class);
JSFUtils jsfUtils = spy(new JSFUtils(/* mocks of dependencies if needed */));
But this is only needed if want to mock the return value of some other method in your class under test to force isolation of your unit.
This is not the case in your example as far as I see. So just write:
//JSFUtils jsfUtils = mock(JSFUtils.class);
JSFUtils jsfUtils = new JSFUtils(/* mocks of dependencies if needed */);
#Test
public void testResolveExpression() {
when(jsfUtils.resolveExpression("expression")).thenAnswer(new Answer<Object>(){
public Object answer(InvocationOnMock invocation){
when(facesContext.getApplication()).thenReturn(app);
when(app.getExpressionFactory()).thenReturn(exFactory);
when(facesContext.getELContext()).thenReturn(elContext);
when(exFactory.createValueExpression(elContext, "expression", Object.class)).thenReturn(valExp);
when(valExp.getValue(elContext)).thenReturn(anyObject());
return valExp.getValue(elContext);
}
});
jsfUtils.resolveExpression(anyString());
verify(jsfUtils).resolveExpression(anyString());
assertNotNull(jsfUtils.resolveExpression(anyString()));
This does not make any sense:
You mock the method of your class under test (cut) and then call that very same method. This way you do not verify the behavior of your cut but the behavior of the mocking framework.
Also you call the method twice within the same test method. You should avoid that.
You should change your test to this:
#Test
public void testResolveExpression() {
// arrange (test case specific setup of mocks and DTOs)
when(facesContext.getApplication()).thenReturn(app);
when(app.getExpressionFactory()).thenReturn(exFactory);
when(facesContext.getELContext()).thenReturn(elContext);
when(exFactory.createValueExpression(elContext, "expression", Object.class)).thenReturn(valExp);
when(valExp.getValue(elContext)).thenReturn(anyObject());
// act (call real method on real object)
Object result = jsfUtils.resolveExpression("a valid input");
// assert
assertNotNull(result );
}