Junit Test cases for update and get - spring-boot

Question

I have these two functions in my userServiceImpl class. I want to write their test cases. I am completely new to this so cannot figure out how to write the jUnit test cases.
public UserDto updateUser(String userId, UserDto user) {
UserEntity userEntity = this.userRepository.findByUserId(userId);
if (userEntity == null)
throw new UsernameNotFoundException("User with ID: " + userId + " not found");
userEntity.setName(user.getName());
userEntity.setCity(user.getCity());
userEntity.setAddress(user.getAddress());
userEntity.setPhoneNumber(user.getPhoneNumber());
UserEntity updatedUserDetails = userRepository.save(userEntity);
return new ModelMapper().map(updatedUserDetails, UserDto.class);
}
#Override
public List<UserDto> getUsers(int page, int limit) {
List<UserDto> returnValue = new ArrayList<>();
Pageable pageableRequest = PageRequest.of(page, limit);
Page<UserEntity> usersPage = this.userRepository.findAll(pageableRequest);
List<UserEntity> users = usersPage.getContent();
//loop on list of users and create new userdto for each user
for (UserEntity userEntity : users) {
UserDto userDto = new UserDto();
BeanUtils.copyProperties(userEntity, userDto);
returnValue.add(userDto);
}
return returnValue;
}
I tried writing the test case for updateUser but it failed
testUpdateUser
final void testUpdateUser() {
when(userRepository.save(any(UserEntity.class))).thenReturn(userEntity);
UserDto userDto = new UserDto();
UserDto storedDetails = userService.updateUser("edsd3445tcd", userDto);
assertNotNull(storedDetails);
}
Please help me with these two test cases.

Answer 1

As discussed in the comments: The method findByUserId of the Mock is called but the call is not part of the teaching. The Mock will return null and therefore we get an UsernameNotFoundException.
Solution: add the missing when(userRepository.findByUserId(...))...;
I also suggest to use an ArgumentCaptor to be able to add some assertions.
Without the capture, you won't see, if the changes will be saved.
Variable userEntity seems to be a member variable. I would rather use two local variables, one to represent the state at the first teaching and one to represent the state at the second teaching.
final void testUpdateUser() {
var id = "edsd3445tcd";
var userEntityBeforeChange = new UserEntity();
userEntityBeforeChange.setId(id);
userEntityBeforeChange.setName("Old Name");
// ... set more attributes ...
var userEntityAfterChange = new UserEntity();
userEntityAfterChange.setId(id);
userEntityAfterChange.setName("Changed Name");
// ... set more attributes ...
when(userRepository.findByUserId(id)).thenReturn(userEntityBeforeChange);
ArgumentCaptor<UserEntity> argument = ArgumentCaptor.forClass(UserEntity.class);
when(userRepository.save(argument.capture())).thenReturn(userEntityAfterChange);
UserDto userDto = new UserDto();
userDto.setName("New Name");
// ... set more attributes ...
UserDto storedDetails = userService.updateUser(id, userDto);
assertEquals(userDto.getName(), argument.getValue().getName());
assertNotNull(storedDetails);
assertEquals(userEntityAfterChange.getName(), storedDetails.getName());
// ... assertions for other attributes ...
}
Testing getUsers works in the same way: Teach the mock that there will be a call of findAll, call getUsers and finish with some assertions.