使用Mockito使用条件循环测试void方法

Question

I have following method which asks for user input until valid user credentials are entered.It then generates id for that user and sets registered =TRUE.

1.How can I check the value of local variable "registered" from my unit test?

2.How can I assert in my test that while loop executed until "registered" became TRUE?

private void register() {

    boolean registered=false;
    while(!registered){
        try {
            String uname =this.read("User Name : ");
            char password[] = this.readPassword();
            String serverURL = this.read("Server URL : ");

            if(!uname.isEmpty() && password!=null && !serverURL.isEmpty()){ 

                registered=this.getUID(uname,password,serverURL);
            }
            if(registered==false)
                System.out.println("\nPlease verify your details and try again!\n");

        } catch (UnsupportedEncodingException e) {} 
        catch(Exception e){}    
    }
    System.out.println("Successful");
}

I have come across usage of ArgumentCaptor to capture variables that a method to be tested, uses to invoke another methods.

e.g verify(mockObj).intArgumentMethod(argument.capture());

However I am not passing variable "registered" to any other method otherwise i would have captured it.

Answer 1

1. You cannot
2. By verification:
   • The loop invariant is that registered is false. So the loop is not entered if it is true
   • The loop is exited
     • at the bodies start (in this case it is true)
     • if a Throwable is thrown, that is not caught by 'catch(Exception e)' (in this case it might be anything)

Anyway - review your testing strategy:

• a function has input parameters and output parameters

• the input should be part of the fixture:

   this.read("User Name : ") this.readPassword() this.read("Server URL : ") this.getUID(uname,password,serverURL) // this may also be viewed as output 

• the output should be part of the assertions

   System.out.println(...) 

The input can be set up by creating anonymous sub classes, eg

fixture = new YourClass {
  public String read(String prompt) {
    return mockedString;
  }
  ...
};

The output can be captured/asserted by a Junit Rule, eg StandardErrorStreamLog

Mockito is not needed with this example method.

Answer 2

Don't test the implementation details, test the behavior given certain input. If the registered variable is supposed to be some sort of output then it shouldn't be a local variable.

One design I like is to use method objects, it is possible to pass arguments at object creation, and an object method can have multiple return values.

class Registrator {
    Registrator(...) { /* assigning needed field */ }

    void register() { /* logic that will mutate internal fields */ }

    boolean registered() { return registered; }
    long triesCount() { return triesCount; }
    // ...
}

And one can adapt the code to use a Report object, on which the register method can append success / failure / more details like reasons / etc.

And the test would be much more easy to write.