Mockito Test Exception Expected

Question

I'm trying to test my service layer and repository in spring-boot, and to do this, I'm using Mockito, as part of my test, I validate any log in request and if the username or password is incorrect, an exception should be thrown.

I'm testing that a user exist and my test passes, but, I can't seem to get my test to pass when a username does not exist. Here is my code for the tets

@Mock
UserRepository userRepository;

@InjectMocks
UserServiceImpl userServiceImpl;

Users mockUser = Mockito.mock(Users.class);

private String username = "real_user";

private String fakeUser = "fake_user";

@Before
public void setup() {
    mockUser.setUsername(username);
    mockUser.setPassword(new BCryptPasswordEncoder().encode("password"));
    mockUser.setEnabled(true);
}

/**
 * This Test Passes
 */
@Test
public void should_LoadUsersByUsername_IfUserExists() {
    Mockito.when(userRepository.findByUsername(username)).thenReturn(mockUser);
    userServiceImpl.loadUserByUsername(username);
    Mockito.verify(userRepository, Mockito.atLeastOnce()).findByUsername(username);
}

/**
 * This Test Fails
 */
@Test(expected = UsernameNotFoundException.class)
public void should_Throw_UserNameNotFoundException_If_UserIsNotFound() {
    Mockito
       .when(userRepository.findByUsername(fakeUser))
       .thenThrow(UsernameNotFoundException.class);
}

This is the code I'm trying to run the test on

@Service
public class UserServiceImpl implements UserService {

@Autowired
UserRepository userRepository;

@Override
public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
    Users user = userRepository.findByUsername(username);
    if (user == null) {//I'm trying to hit this line with my test that fails
        throw new UsernameNotFoundException("The user was not found");
    }
    return user;
}

When I run my tests I get the following

java.lang.AssertionError: Expected exception: org.springframework.security.core.userdetails.UsernameNotFoundException
    at org.junit.internal.runners.statements.ExpectException.evaluate(ExpectException.java:32)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:79)
    at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:85)
    at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:39)
    at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:538)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:760)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:460)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:206)

The line below is makes me confused because on my test I am stating that the UsernameNotFoundException should be thrown if the user does not exist

java.lang.AssertionError: Expected exception: org.springframework.security.core.userdetails.UsernameNotFoundException

I followed the tutorial found here on number 2

Non-Void Return Type

but no luck, I know that I can accomplish my goal using JUnit but I want to try and do this using Mockito first

I know I'm missing something, can anyone please help me understand whats happening here

Answer 1

In your failing testcase you are not calling loadUserByUsername function at all. This should work.

@Test(expected = UsernameNotFoundException.class)
public void should_Throw_UserNameNotFoundException_If_UserIsNotFound() {
    Mockito
       .when(userRepository.findByUsername(fakeUser))
       .thenThrow(UsernameNotFoundException.class);
   userServiceImpl.loadUserByUsername(fakeUser);
}

Since you don't call the function, exception is never thrown, But you have told Mockito that there will be an exception and hence Mockito says

java.lang.AssertionError: Expected exception: org.springframework.security.core.userdetails.UsernameNotFoundException

Answer 2

You need to call the function you are trying to test. Looks like you missed this in the failing test -

userServiceImpl.loadUserByUsername(username);

Answer 3

I would like to tell you that there are better way to verify the exception then @Test(expected). Lets look at the assertj sample

assertThatThrownBy(() -> userRepository.findByUsername(fakeUser)) 
        .isInstanceOf(UsernameNotFoundException.class)
        .hasMessage("some message")
        .hasNoCause();