Qfyilyi

I have EmailService class which has method sendEmail(Person person, Location location); Location is enum - Location.EUROPE and Location.USA. Based on the location I choose different email template, that is I have private method inside EmailService:

 private String chooseEmailTemplate(Location location){

    if(location.equals(Location.EUROPE))

      return "templateEU";

    return "templateUSA";

  }

inside the sendEmail(Person person, Location location) I call chooseEmailTemplate(location) and select the right template string.

public void sendEmail(Person person, Location location) {

    String name = person.getName();

    String age = person.getAge();

    ....



    String emailTemplate = chooseEmailTemplate(location);



    String body = templateEngine.process(emailTemplate, content);

    ...

    //do something else and send the email

  }

templateEngine is injected @Qualifier private TemplateEngine templateEngine;

UPDATE:
Inside EmailService I have the following method:

public void setTemplateEngine(TemplateEngine templateEngine) {

    this.templateEngine = templateEngine;

  }

And I am injecting it the following way:

 @Autowired

  @Qualifier("textTemplateEngine")

  private TemplateEngine templateEngine;

Inside EmailServiceTest this used to be my setUp():

@Before

  public void setup() {

    ThymeleafConfig tc = new ThymeleafConfig();

    templateEngine = tc.templateEngine();



    MockitoAnnotations.initMocks(this);

    emailService.setTemplateEngine(templateEngine);

  }

Yes, I know that templateEngine is not a mock but an actual object, and hence the error on line verify(templateEngine).process("templateEU", any(Content.class));. But when I change it to a mock, I get NullpointerException.

End Of the Update

In my test, I want to test that when Location is Europe it will process templateEU and when location is USA it will process templateEU.

I tried the following:

@Test

  public void shouldCallTemplateEngineWithEuropeTemplate(){

    location = Location.EUROPE;



    //throws null pointer exception

    emailService.sendEmail(any(Person.class), location);



    verify(templateEngine).process("templateEU", any(Content.class));

  }

But it complains that I am mocking the Person parameter. At this particular test, I don't care which Person object I am sending, I only care about the Location enum.

argument matchers are used when arranging or asserting member calls on mocked dependencies.

They are not used/passed as arguments when exercising the member under test and will actually pass the default value of the type, which in this case would be null. Hence the null reference exception when

String name = person.getName();

is called.

Instead, create an instance of the parameter and pass that to the subject under test.

//Arrange

location = Location.EUROPE;

Person person = new Person();



//Act

emailService.sendEmail(person, location);



//Assert

//...

or just mock the class and pass that instead to avoid null reference errors

//Arrange

location = Location.EUROPE;

Person person = mock(Person.class);



//Act

emailService.sendEmail(person, location);



//Assert

//...

making sure to setup any member calls on Person that would cause issues if not configured.

As for the template issue, you would should mock the template so that the unit test is truly an isolated test.

@Before

public void setup() {    

    templateEngine = mock(TemplateEngine.class); //Use a mock



    MockitoAnnotations.initMocks(this);

    emailService.setTemplateEngine(templateEngine);

}

And

verify(templateEngine).process("templateEU", any(Content.class));

behaves as intended.