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Mockito - mock ApplicationContext

I have a Springboot application that looks up the bean from the ApplicationContext at runtime based on the input parameter passed by the user. For this method, I am trying to write Mockito test cases but it is not working and throws NullPointerException.
The class which bootstraps the application:
#SpringBootApplication
public class MyApplication {
private static ApplicationContext appContext;
public static void main(String[] args) {
appContext = SpringApplication.run(MyApplication.class, args);
}
public static ApplicationContext getApplicationContext() {
return appContext;
}
}
Class for which I am trying to write the test cases:
#Service
public class Mailbox {
#Autowired
MailProcessor processor;
public void processUserInput(Envelope object) {
processor.setCommand(MyApplication.getApplicationContext().getBean(object.getAction(), Command.class));
processor.allocateEnvelopes(object);
}
}
And my test case is as below:
#RunWith(MockitoJUnitRunner.class)
#SpringBootTest
#ActiveProfiles("test")
public class MailboxTest {
#Mock
MailProcessor processor;
#InjectMocks
Mailbox mailbox;
#Test
public void testProcessUserInput() {
Envelope message = new Envelope();
message.setAction("userAction");
message.setValue("userInput");
doNothing().when(processor).setCommand(any());
doNothing().when(processor).allocateEnvelopes(any());
mailbox.processUserInput(message);
Mockito.verify(processor).allocateEnvelopes(any());
}
}
Whenever I run the test cases it gives the NullPointerException at processor.setCommand(MyApplication.getApplicationContext().getBean(object.getAction(), Command.class)); in Mailbox class. How can I mock the ApplicationContext lookup? Am I missing any mocking step?

Spring wise your code doesn't look good, and in particular is not unit testable. I'll explain:
Your Mailbox service should not be aware of MyApplication at any level. It is an entry point of spring boot application and your business logic should not depend on that.
Its true that you can inject the application context directly into the class. See an example below. Another (more "old-school") option here is using ApplicationContextAware interface in the Mailbox service (see this example). However, its still a bad code IMO:
#Service
public class Mailbox {
private final ApplicationContext ctx;
...
public Mailbox(ApplicationContext ctx) {
this.ctx = ctx;
}
...
}
Even if you resolve it, in general its not a good idea to depend on the ApplicationContext as well. Because this way you become spring dependent and there is no reason to do that in the Mailbox class. The class will become unit testable though.
In terms of resolution:
In spring you can inject a Map<String, Command> into the mailbox (Its a built-in feature in spring) so that the key of the map will be a bean name, exactly an action of your envelop.
So here is the solution (simplified in places not relevant to injection, just to illustrate the idea):
public interface Command {
void execute();
}
#Component("delete") // note this "delete" word - it will be a key in the map in the Mailbox
public class DeleteMailCommand implements Command {
#Override
public void execute() {
System.out.println("Deleting email");
}
}
#Component("send")
public class SendMailCommand implements Command{
#Override
public void execute() {
System.out.println("Sending Mail");
}
}
Note, that all the commands must be driven by spring (which seems to be your case anyway).
Now, the Mailbox will look like this:
#Service
public class Mailbox {
private final Map<String, Command> allCommands;
private final MailProcessor processor;
// Note this map: it will be ["delete" -> <bean of type DeleteMailCommand>, "send" -> <bean of type SendMailCommand>]
public Mailbox(Map<String, Command> allCommands, MailProcessor mailProcessor) {
this.allCommands = allCommands;
this.processor = mailProcessor;
}
public void processUserInput(Envelope envelope) {
Command cmd = allCommands.get(envelope.getAction());
processor.executeCommand(cmd);
}
}
This solution is easily unit testable, because you can populate the map with mock commands if you wish and there is no need to deal with the application context.
Update
I took a look on your test now, and it's also not really good, sorry :)
#RunWith(MockitoJUnitRunner.class) is used to run unit tests (without spring at all). There is no point in placing this annotation in conjunction with #SpringBootTest which runs a full-fledged system test: starts the whole spring boot application, loads configurations and so forth.
So make sure what kind of tests you want to run and use the appropriate annotations.

Can't say for sure without debugging but it looks like MyApplication.getApplicationContext() is returning null.
Instead of storing it in a static variable you should try injecting the ApplicationContext in your #Service class where you need it:
#Autowired
private ApplicationContext appContext;

Try initializing mailbox object by injecting processor before first test.
mailbox = new Mailbox(processor);

How to create a test in Springt Boot that calls a service which includes constructor injection?

I'm trying to write a test in a Spring-Boot project. My problem is that I can't use my service that includes a constructor injection.
Depending on what I try I get errors like java.lang.IllegalStateException: Failed to load ApplicationContexts or NullPointerExceptions.
My first try was to change the constructor injection in my service to a field injection. But after reading this post I decided to change it back to the previous way.
Then I searched for examples but couldn't find something that was helpful.
Following are the relevant code snippets. If more code is needed I would provide it.
The service class with the constructor injection:
PlayerServiceImpl.java
#Service
public class PlayerServiceImpl implements PlayerService {
private PlayerRepository playerRepository;
private CompanyService companyService;
private CompanyResourceService companyResourceService;
#Autowired
public PlayerServiceImpl(PlayerRepository thePlayerRepository, CompanyService theCompanyService,
CompanyResourceService theCompanyResourceService) {
this.playerRepository = thePlayerRepository;
this.companyService = theCompanyService;
this.companyResourceService = theCompanyResourceService;
}
...
}
The test class im trying to create:
PlayerServiceImplIntegrationTest.java
#RunWith(SpringRunner.class)
#SpringBootTest
public class PlayerServiceImplIntegrationTest {
#TestConfiguration
static class PlayerServiceImplTestContextConfiguration {
private PlayerRepository playerRepository;
private CompanyService companyService;
private CompanyResourceService companyResourceService;
#Bean
public PlayerService playerService() {
return new PlayerServiceImpl(playerRepository, companyService, companyResourceService);
}
}
#Autowired
private PlayerService playerService;
#MockBean
private PlayerRepository playerRepository;
#Before
public void setUp() {
Player max = new Player("MaxMustang", "test123", "MaxMustang",
"max.mustang#test.com", new Date(System.currentTimeMillis()), 1, 0,
new BigDecimal("0.00"), new BigDecimal("0.00"), 0, 0);
Mockito.when(playerRepository.findByUserName(max.getUserName()))
.thenReturn(max);
}
#Test
public void whenFindById_thenReturnPlayer() {
String userName = "MaxMustang";
Player found = playerService.findByUserName(userName);
assertThat(found.getUserName()).isEqualTo(userName);
}
}
In my test, I'm trying to create a player object and receive it. It's just my first test in Spring Boot. And my main goal was to just get the test running.
And the original test is from Baeldung from "5. Mocking with #MockBean". But while experimenting around, I added or changed a few things.
If I missed a post pointing at the same problem I would be glad to be informed about that.
Also, I would appreciate it if someone can tell me if the arguments in the constructor of my service are too much or still in an "ok" range.

You have to make the configuration bean primary and also use constructor injection on that method:
#TestConfiguration
static class PlayerServiceImplTestContextConfiguration {
#Bean
#Primary
public PlayerService playerService(PlayerRepository playerRepository,
CompanyService companyService, CompanyResourceService companyResourceService) {
return new PlayerServiceImpl(playerRepository, companyService, companyResourceService);
}
}
Without primary you will have two beans of same type floating around and you dont use #Qualifier here. Also you cannot #Autowire beans in a configuration class thats why you need to use constructor injection.

Mockito when isn't replacing original method behaviour

I got 2 modules User and Email, both of them have 1 entry point which is a facade, rest is package scoped. The configuration is done in 2 classes
#Configuration
class UserConfiguration {
#Bean
UserFacade userFacade(UserRepository repository, EmailFacade emailFacade) {
return new UserFacade(repository, emailFacade);
}
}
#Configuration
class EmailConfiguration {
#Bean
EmailFacade emailFacade(EmailSender emailSender) {
return new EmailFacade(emailSender);
}
}
Now, I want to write tests that don't require Spring to start. I implemented a simple InMemoryRepository to make this happen
#RunWith(MockitoJUnitRunner.class)
public class RegisterUserTest {
#Mock
private EmailFacade emailFacade = new EmailFacade(new FakeEmailSender());
#InjectMocks
private UserFacade userFacade = new UserConfiguration().userFacade(new InMemoryUserRepository(), emailFacade);
#Before
public void setUp() {
MockitoAnnotations.initMocks(this);
}
}
I need some fake objects to instantiate EmailFacade so I wrote fake implementation
public class FakeEmailSender implements EmailSender {
#Override
public void sendEmail(EmailMessage emailMessage) throws RuntimeException {
}
}
In that scenario, I'm testing User domain, so I want to mock Email anyways.
I wrote a test to check if it works
#Test
public void shouldReturnSendingFailed() {
Mockito.when(emailFacade.sendUserVerificationEmail(Mockito.any())).thenReturn(Either.left(EmailError.SENDING_FAILED));
assertThat(userFacade.registerNewUser(RegisterUserDto.builder()
.username(USERNAME_4)
.email(VALID_EMAIL)
.password(VALID_PASSWORD).build()).getLeft(), is(EmailError.SENDING_FAILED));
}
But it isn't... after running this test I got
java.util.NoSuchElementException: getLeft() on Right
edit#
regiserNewUser() method
Either<DomainError, SuccessMessage> register(RegisterUserDto registerUserDto) {
if(userRepository.findUser(registerUserDto.getUsername()).isPresent())
return Either.left(UserError.USERNAME_ALREADY_EXISTS);
var userCreationResult = User.createUser(registerUserDto);
var savedUser = userCreationResult.map(this::saveUser);
var emailDto = savedUser.map(this::createVerificationEmail);
return emailDto.isRight() ? emailFacade.sendUserVerificationEmail(emailDto.get())
: Either.left(emailDto.getLeft());
}
Edit2#
With following test configuration
#RunWith(MockitoJUnitRunner.class)
public class RegisterUserTest {
#Mock
private EmailFacade emailFacade;
#InjectMocks
private UserFacade userFacade = new UserConfiguration().userFacade(new InMemoryUserRepository(), emailFacade);
#Before
public void setUp() {
MockitoAnnotations.initMocks(this);
}
}
I got nullpointer here, last line of registerNewUser().

Try running this code
#RunWith(MockitoJUnitRunner.class)
public class RegisterUserTest {
#Mock
private EmailFacade emailFacade;
private UserFacade userFacade;
#Before
public void setUp() {
userFacade = new UserConfiguration().userFacade(new InMemoryUserRepository(), emailFacade);
}
}
There are a few issues with your code:
You initialize your mocks twice. You don’t need to call initMocks in the setUp method if you are using Mockito runner
You are trying to inject mocks to already initialized object. But the field you are trying to inject is also passed to the constructor. Please read #InjectMocks doc, to check the strategies used to inject the mocks:
constructor (not used here, already initialized object)
setter (do you have one?)
field (is it not final)
There are details to each strategy (see my questions above). If no staregy is matched, Mockito will fail silently. The fact that you are passing an object in constructor, and rely on setter or field injection afterwards makes this code unnecesarily complex.

Mockito to test an autowired field

public interface Dummy {
public returnSomething doDummyWork(arg1, agr2);
}
public class A implements Dummy {
#AutoWired
PrintTaskExecutor printTaskExecutor;
public returnSomething doDummyWork(arg1, agr2) {
callingVoidMethod();
return something;
}
public void callingVoidMethod() {
printTaskExecutor.printSomething(arg1, arg2);
}
}
public class testDummy {
#Autowired
Dummy dummyA//this bean is configured in ApplicationContext.xml and it works fine.
#Mock
PrintTaskExecutor printaskExecutor;
#Before
public void initMocks() {
MockitoAnnotations.initMocks(this);
printaskExecutor = Mockito.mock(PrintTaskExecutor.class);
Mockito.doNothing().when(printaskExecutor).printSomething(anyString(), anyString());
}
#Test
Public void testA
{
Dummy.doDummyWork(arg1, arg2);//I m giving actual arguments
//instead of moocking it calls the original method.
Mockito.verify(printaskExecutor, times(1)).printSomething(anyString(), anyString());
}
}
I have an autowired TaskExecutor in the class I m testing and I want to mock it.I have tried this in my code and It calls the actual method instead of do nothing and in the verify it errors out saying no interactions happened. How should I handle this situation?

I try to avoid using Mockito and Bean Containers together in one test. There are solutions for that problem. If you use Spring you should use #RunWith(SpringJUnit4Runner.class). More on this subject: Injecting Mockito mocks into a Spring bean
The clean way: Actually your class testDummy does not test Dummy but A. So you can rewrite your class in following way:
public class testA {
#Mock
PrintTaskExecutor printTaskExecutor;
#InjectMocks
A dummyA;
...
BTW: #Mock together with initMocks(this) and printaskExecutor = Mockito.mock(PrintTaskExecutor.class); do the same, you can skip the latter statement.

NoSuchBeanDefinitionException for dependencies of mocked beans

I am attempting to use mocks in my integration test and am not having much luck. I am using Spring 3.1.1 and Mockito 1.9.0, and the situation is as follows:
#Component
public class ClassToTest {
#Resource
private Dependency dependency;
}
and
#Component
public class Dependency {
#Resource
private NestedDependency nestedDependency;
}
Now, I want to do an integration test of ClassToTest using Spring's JavaConfig. This is what I have attempted, and it doesn't work:
#Test
#ContextConfiguration
public class ClassToTestIntegrationTest {
#Resource
private ClassToTest classToTest;
#Resource
private Dependency mockDependency;
#Test
public void someTest() {
verify(mockDependency).doStuff();
// other Mockito magic...
}
#Configuration
static class Config {
#Bean
public ClassToTest classToTest() {
return new ClassToTest();
}
#Bean
public Dependency dependency() {
return Mockito.mock(Dependency.class);
}
}
}
I have simplified my setup to make the question easier to understand. In reality I have more dependencies and only want to mock some of them - the others are real, based on config imported from my prod #Configuration classes.
What ends up happening is I get a NoSuchBeanDefinitionException saying that there are no beans of type NestedDependency in the application context. I don't understand this - I thought Spring would receive Mockito's mocked instance of Dependency and not even look at autowiring it. Since this isn't working I end up having to mock my entire object graph - which completely defeats the point of mocking!
Thanks in advance for any help!

I had the same problem and I found another solution.
When Spring instantiate all your beans, it will check if it's a Mockito Mock and in this case, I return false for injection property. To use it, just inject it in a Spring context
Code below:
public class MockBeanFactory extends InstantiationAwareBeanPostProcessorAdapter {
private static final MockUtil mockUtil = new MockUtil();
public MockBeanFactory() {
super();
}
#Override
public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
return !mockUtil.isMock(bean);
}
}

What Mockito does when mocking classes is it creates a subclass using cglib having some fancy name like: Dependency$EnhancerByMockito (IIRC). As you probably know, subclasses inherit fields from their parent:
#Component
public class Dependency {
#Resource
private NestedDependency nestedDependency;
}
public class Dependency$EnhancerByMockito extends Dependency{
//...
}
This means Spring still sees the field in base class when presented with mock. What you can do:
Use interfaces, which will cause Mockito to employ dynamic proxies rather than CGLIB-generated classes
Mock NestedDependency - I know it will just cascade the problem one level further
Disable #Resource annotation scanning for tests