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Mockito.mockConstruction does not return the mocked object

I don't want to use powermock anymore. Because junit5 started mocking static classes. So i am trying to get rid of powermock methods.
As you know, you can create an instance of a class with whenNew keyword. So i decided to use " mockConstruction " . But mockConstruction does not return the mocked object. It doesn't go inside the try block.
This is my BeforeEach method:
#BeforeEach
void setUp() {
partUnlinkService =
spy(new PartVideoUnlinkService(part1, part2,
part3));
}
This is my test method:
#Test
void shouldThrowException() throws Exception {
//given
UrlLinkDto urlLinkDto =
UrlPartLinkDto.builder().callId("333").videoId("5555544").build();
ArgumentCaptor<UrlPartLinkDto> argumentCaptor = ArgumentCaptor.forClass(UrlPartLinkDto.class);
//when
try (MockedConstruction<ObjectMapper> ignoredVariable = mockConstruction(ObjectMapper.class,
(objectMapper, context) -> {
//then
partUnlinkService.unlink(urlLinkDto, false);
verify(partLogCheckService, times(1)).checkForExistingVideo(
urlLinkDto.getVideoId());
verify(objectMapper, times(1)).writeValueAsString(argumentCaptor.capture());
Throwable throwable =
catchThrowable(() -> objectMapper.writeValueAsString(argumentCaptor.capture()));
assertThat(throwable).isInstanceOf(JsonProcessingException.class);
})) {
}
}
Any help would be appreciated.

You can access mocks that were created during the instantiation of your objects via MockedConstruction.constructed() method. It represents a collection of mocks that are created after each constructor's execution. If your object will be instantiated 3 times MockedConstruction<T>.constructed() will return 3 different mock objects for each instantiation.
According to documentation MockedConstruction<T>
Represents a mock of any object construction of the represented type.
Within the scope of the mocked construction, the invocation of any
interceptor will generate a mock which will be prepared as specified
when generating this scope. The mock can also be received via this
instance.
Simple implementation with comments below shows how to get mocks from MockedConstruction and verify them:
public class A {
private final String test;
public A(String test) {
this.test = test;
}
public String check() {
return "checked " + this.test;
}
}
public class TestService {
public String purchaseProduct(String param) {
A a = new A(param);
return a.check();
}
}
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.mockito.MockedConstruction;
import org.mockito.Mockito;
import static org.mockito.Mockito.*;
public class ConstructorMockTest {
private MockedConstruction<A> mockAController;
#BeforeEach
public void beginTest() {
//create mock controller for all constructors of the given class
mockAController = Mockito.mockConstruction(A.class,
(mock, context) -> {
//implement initializer for mock. Set return value for object A mock methods
when(mock.check()).thenReturn(" Constructor Mock A ");
});
}
#Test
public void test() {
//each instantiation of class A will return new mock, which initialized by initializer from beginTest method
//new mock will be stored to mockAController.constructed() collection of mocks
A aObject = new A("test");
//ensure that method check() returns mocked value
Assertions.assertEquals(aObject.check(), " Constructor Mock A ");
//get just created mock for class A from controller. It will be first element of mockAController.constructed() collection
A aMock = mockAController.constructed().get(0);
//ensure that we get correct mock from mock controller, that it is equal from new created object
Assertions.assertEquals(aMock, aObject);
//verify that check method was executed on Mock
verify(aMock, times(1)).check();
//create new A object, new mock created and stored to mockAController.constructed()
A aObject2 = new A("test");
//ensure that method check() returns mocked value
Assertions.assertEquals(aObject2.check(), " Constructor Mock A ");
//get just created mock for class A from controller, it will be second object from constructed collection
A aMock2 = mockAController.constructed().get(1);
//ensure that we get correct mock from mock controller, that it is equal from just created A object
Assertions.assertEquals(aObject2, aMock2);
//verify that check method was executed on Mock
verify(aMock2, times(1)).check();
//Example of testing service which creates A object
TestService service = new TestService();
String serviceResult = service.purchaseProduct("test");
//ensure that service returned value from A mock
Assertions.assertEquals(serviceResult, " Constructor Mock A ");
//get just created mock for class A from controller, it will be third object from constructed collection
A aMock3 = mockAController.constructed().get(2);
//verify that check method was executed on Mock
verify(aMock3, times(1)).check();
}
#AfterEach
public void endTest() {
mockAController.close();
}
}
Let's rewrite your test. I do not have the full code, but I will try to create an example with comments:
#Test
void shouldThrowException() throws Exception {
//given
UrlLinkDto urlLinkDto =
UrlPartLinkDto.builder().callId("333").videoId("5555544").build();
ArgumentCaptor<UrlPartLinkDto> argumentCaptor = ArgumentCaptor.forClass(UrlPartLinkDto.class);
try (MockedConstruction<ObjectMapper> objectMapperMockedConstruction = mockConstruction(ObjectMapper.class,
(objectMapper, context) -> {
//initialize ObjectMapper mock to throw exception when argumentCaptor will come to writeValueAsString method
doThrow(JsonProcessingException.class).when(objectMapper).writeValueAsString(argumentCaptor.capture());
})) {
//execute service for testing and catch exception
Throwable throwable = catchThrowable(() -> partUnlinkService.unlink(urlLinkDto, false));
//verify that inner service was executed
verify(partLogCheckService, times(1)).checkForExistingVideo(urlLinkDto.getVideoId());
//verify that ObjectMapper was instantiated
Assertions.assertEquals(1, objectMapperMockedConstruction.constructed().size());
//get mock of ObjectMapper which was instantiated during service execution
ObjectMapper objectMapper = objectMapperMockedConstruction.constructed().get(0);
//verify that writeValueAsString was executed
verify(objectMapper, times(1)).writeValueAsString(argumentCaptor.capture());
//check that exception is correct
assertThat(throwable).isInstanceOf(JsonProcessingException.class);
}
}

I think I have the same question as you, hope someone can solve our problem.
In my case, I also want to got a return object like PowerMock.whenNew().withArguments().thenReturn(someThing), I try a lot of times but it failed.
I think mockConstruction just only can mock their behavior, can't verify their result like powerMock, and I couldn't find any articles or answers.
below is my post link :
Junit 5 use mockConstruction().withSetting().useConstructor() instead of PowerMock.whenNew().withArguments()

Mocking not able to mock method call

I am trying to mock a call in my test but I am getting a error as its calling the real method than mocking it.
This is my method
#Value("${omega.aws.nonprod-profile}")
private String nonProdProfile;
#Autowired
AwsService awsService;
public List<SecurityGroup> getAllSecurityGroups() {
AmazonEC2 ec2 = configSetter();
return awsService.getAllSecurityGroups(ec2);
}
protected AmazonEC2 configSetter() {
ProfileCredentialsProvider credentials = new ProfileCredentialsProvider(nonProdProfile);
ClientConfiguration clientCfg = new ClientConfiguration();
clientCfg.setProxyHost(this.proxyHost);
clientCfg.setProxyPort(Integer.valueOf(proxyPort));
clientCfg.setProtocol(Protocol.HTTPS);
return new AmazonEC2Client(credentials, clientCfg);
}
Here is my test class
#InjectMocks
private AwsConfigurationLocal subject;
#Mock
private AwsService awsService;
#Test
public void TestgetAllSecurityGroups() throws Exception {
ec2 = Mockito.mock(AmazonEC2Client.class);
securityGroup = new SecurityGroup();
List<SecurityGroup> result = Collections.singletonList(securityGroup);
Mockito.when(awsService.getAllSecurityGroups(ec2)).thenReturn(result);
List<SecurityGroup> actual = subject.getAllSecurityGroups();
assertThat(actual, CoreMatchers.is(equals(result)));
}
The test actually calls the protected method configSetter and fails when setting a proxy. Help me understand what I am doing wrong here.

subject.getAllSecurityGroups(); calls real configSetter() which returns real AmazonEC2 which in turn is passed on to awsService.getAllSecurityGroups(ec2);. The parameter doesn't match your mock ec2 so the default mock implementation is returned (I guess it's null) as a actual.
So the issue is: there is nothing that would prevent real implementation of configSetter() to be called.
If you annotate subject with #Spy and do
Mockito.when(subject.configSetter()).then(ec2);
it should work as expected.
That being said there's a lot of set up done only to check simple invocation being delegated. This is due intermixing of two responsibility in AwsConfigurationLocal - creation of AmazonEC2Client and providing getAllSecurityGroups(). If you move the former into separate class (let's say AmazonEC2ClientFactor) everything should fall in place.

Try using powerMockito to return the mocked instance of AmazonEC2
#RunWith(PowerMockRunner.class)
#PrepareForTest({AwsConfigurationLocal.class})//assuming this is your test class
#InjectMocks
private AwsConfigurationLocal subject=PowerMockito.spy(AwsConfigurationLocal.class);//or try Mockito.spy instead, whichever works
#Test
public void TestgetAllSecurityGroups() throws Exception {
ec2 = Mockito.mock(AmazonEC2Client.class);
PowerMockito.doReturn(ec2).when(subject).configSetter().withNoArguments();
//your code
}

How to mock a method call within a method for which i am writing junit test

Could someone help me with mocking a method call within a method
my code is like :
public class Service {
public List<Bean> Filter(Bean bean){
List<Bean> Filtered_List = getUtilityService.getBeanList();
//Do something
return beanList;
}
}
Now i want to write test case for Service class . How can i mock :
List Filtered_List = getUtilityService.getBeanList(); and set values in it.

The clean solution is to extract UtilityService to a field and pass a mock to the constructor.
public class Service {
private UtilityService utilityService;
public Service(UtilityService utilityService) {
this.utilityService = utilityService;
}
public List<Bean> Filter(Bean bean){
List<Bean> filteredList = utilityService.getBeanList();
//Do something
return beanList;
}
}
You can also introduce a UtilityServiceFactory and have a utilityServiceFactory field in the Service.
public class Service {
private UtilityServiceFactory utilityServiceFactory;
public Service(UtilityServiceFactory utilityService) {
this.utilityServiceFactory = utilityServiceFactory;
}
public List<Bean> Filter(Bean bean){
List<Bean> filteredList = utilityService.create().getBeanList();
//Do something
return beanList;
}
}
If getUtilityService is located in Service class, there is also a dirty solution: partial mock. But I do not recommend it. It's better to refactor your code and use one of previous approaches.
EDIT:
Constructor injection with #InjectMocks is not the best idea but here you are:
import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.BDDMockito.given;
//other imports
#RunWith(MockitoJUnitRunner.class)
public class ServiceTest {
#Mock
UtilityService utilityService;
#InjectMocks
Service service = new Service(null);
#Test
public void shouldFilterBeans() throws Exception {
//given
given(utilityService.getBeanList()).willReturn(asList(new Bean()));
//when
List<Bean> result = service.filter(new Bean());
//then
assertThat(result).hasSize(1); //probably you want to check something else
}
}

to test a method including its own parameter and return value, like the Filter method in your code, it's enough to just pass a Bean instance to it, and then assert the returned List<Bean> object equals to your expected result. generally, for this kind of method, i think it's no need to use mock frameworks.
but if you really want to test the getUtilityService().getBeanList() method call, you should refactor your code:
addfield UnitilityService service and its corresponding setter method in your class Service
in your unit test code, inject a mocked service using the setter method to the object under test and given a returning value for its getBeanList() method, then invoke your Filter method, finally, verify the method call. for the detailed implementation, you can refer the answer of #woru.

How do I mock a method using EasyMock

User getUser(int id) {
User user = service.get( id );
if( user != null ) {
user.Stuff = getUserStuff( id );
return User;
}
throw new NotFoundException();
}
Stuff getUserStuff( int id ) {
stuffGetter.getStuff( id ); // stuff getter makes a rest call
return Stuff;
}
Using EasyMock, how would i test the getUser(id) method. The confusing part for me is that getUserStuff(id) makes an external call which I dont want to make when testing getUser.

As mentioned by other users in the comments, you need to provide mock instances of the objects that are making the calls that you wish to mock out.
So within getUser(id) I can see a call to an object called service which should be mocked out. So use a mock instance of the service class and then the call to get(id) can be mocked out.
Then within the getUserstuff(id) method, it uses a stuffGetter object which could be mocked out again. Then the method being called could have expectations set up for it.
(An alternative to this could also be to set up a partial mock and mock the getUSerstuff(id) method all together, but this is a bit beyond what you're looking to do I think)
With those things in mind, I created the following class to test your described use case:
public class ClassToTest {
private final Service service;
private final StuffGetter stuffGetter;
public ClassToTest() {
this( new Service(), new StuffGetter() );
}
public ClassToTest(final Service service, final StuffGetter stuffGetter) {
this.service = service;
this.stuffGetter = stuffGetter;
}
public User getUser(final int id) {
final User user = this.service.get( id );
if( user != null ) {
user.stuff = getUserStuff( id );
return user;
}
throw new NotFoundException();
}
public Stuff getUserStuff( final int id ) {
return this.stuffGetter.getStuff( id );
}
}
Having the constructors set up like this gives me the ability to set up mock instances of the dependencies within the tests. So what follows is a test for the getUser(id) method that uses mocks for the two objects. It uses the basic EasyMock concepts of expect, replay and verify.
Create mock instances for the objects you need to mock the method calls on, in this case the service and the stuffGetter.
Write expectations for the method calls using the expect method. This is where you specify what will be returned if the method you are mocking is not a void method.
Replay the mock objects, in this case replay both of them. This means you can no longer add any expectations because the mocks are no longer in record mode for recording expectations.
Execute your tests.
Verify that the expected method calls on your mocks were executed as desired.
The tests looks like this:
import static org.junit.Assert.assertEquals;
import org.easymock.EasyMock;
import org.junit.Test;
public class ClassToTestTest {
#Test
public void thatGetIdCallsExpectedMockMethods() {
final User user = new User();
final Stuff userStuff = new Stuff();
final Service mockService = EasyMock.createMock(Service.class);
final StuffGetter mockStuffGetter = EasyMock.createMock(StuffGetter.class);
EasyMock.expect( mockService.get(15) ).andReturn( user );
EasyMock.expect( mockStuffGetter.getStuff(15) ).andReturn( userStuff );
EasyMock.replay( mockService, mockStuffGetter );
final ClassToTest classToTest = new ClassToTest( mockService, mockStuffGetter );
final User returnedUser = classToTest.getUser(15);
assertEquals(returnedUser, user);
assertEquals(returnedUser.stuff, userStuff);
EasyMock.verify( mockService, mockStuffGetter );
}
}

Mock / stub with integration testing in Java

I'm using rest-assured for integration testing on my endpoints. One of the endpoints has a dependency to another resource (it calls another API conditionally). Is there a way for me to stub out the API call so I can write a test for that case?

interface IDataProvider {
string RetrieveData();
}
class StandardDataProvider : IDataProvider {
public string RetrieveData(){
// call to API
}
}
class Program {
private IDataProvider _dataProvider;
public Program(IDataProvider provider = null) {
_dataProvider = provider ?? new StandardProvider();
}
public void MethodToTest(){
var data = _dataProvider.RetrieveData();
// do your thing
}
}
In the tests you can mock the data by creating your own IDataProvider object and working with its data.
class TestDataProvider : IDataProvider {
public string RetrieveData(){
return "my own data";
}
}
class Test {
[TestMethod]
public void TestProgram(){
var obj = new Program(new TestDataProvider);
var result = obj.MethodToTest();
// asserts
}
}

Lets say your code calls endpointB internally via http, you can stub that api by using https://github.com/katta/fakerest or https://stubby4j.com .So when your code makes a call internally to the another api, it will hit these stubs, which will return a dummy response always. Hope this helps.