Spring MVC write unit test for service layer which returns a view

Question

I have to unit test my service layer but I don't know how to do it as I am new to SpringMvc.

Here is the method I want to test:

@Override
public String update(String username, User newUserData, BindingResult result, Model model) {
    if (result.hasErrors()) {
        updateModelData(model, "", result.getAllErrors());
        return HOME_VIEW_NAME;
    }

    User foundUser = this.userRepository.findByUsername(username);
    if (foundUser == null) {
        throw new UserNotFoundException(username);
    }

    String queryResult = String.format("UPDATED SUCCESSFULLY: \n Old User: %s", foundUser);
    foundUser.setPassword(encryptPassword(newUserData.getPassword()));
    foundUser.setStatus(newUserData.getStatus());
    queryResult += String.format("New User: %s", foundUser);

    this.userRepository.save(foundUser);

    updateModelData(model, queryResult, new ArrayList<>());
    return HOME_VIEW_NAME;
}

First - I would like to know if it is a good idea to keep the Model, BindingResult and return a page in the Service layer? If no, why not?

Second - How should I test this method correctly?

Thank you!

Answer 1

I think that it's best to return pages in the controller. I believe the Spring developers created such annotations @Component, @Repository, @Service, @Controller is to also provide context for whichever layer that specific component belongs to. You can check this discussion on SO regarding that.

On your second question, you may want to check out the Spring MVC test framework. You may want to check out MockMvc, there are tons of references in the documentation as well as on the Spring projects repository.

I think you'd need something like the snippet below if you'd like to test your scenario where it went to the correct view after updating:

MockMvc mockMvc;

mockMvc.perform(get("/path/to/update/resource"))
            .andExpect(status().isOk())
            .andExpect(modelAndView().getViewName().isEqualTo("your_view_name"));