[FIXED] JUnit testing / calling function few times

Issue

I am extracting concept from a single page and that page is being used in different functions, so i have created a function that assigns the value if value hasn't been assigned yet.

public String text() {                               
    if (text.isPresent()) {                          
        return text.get();                           
    }                                                
    this.text = Optional.of(extractText(pdDocument));
    return text.get();                               
}

I would like to create a test that checks that the function is being called once and the context is shared between the functions that doing some functionality in the same context

Here is an example when text() is being called twice

private Optional<String> packingListNet() {           
    return locatePattern(text(), PACKING_LIST_NET);   
}  

private Optional<String> packingListNumber() {        
    return locatePattern(text(), PACKING_LIST_NUMBER);
}                  

Would be grateful for any information, thank you

Solution

The technical answer: you could use a mocking library, such as PowerMockito, to create mocked instances of the Optional class. And when you have a mock object, you can instruct the mock how to react to method calls. Then you need to "get" the mocked Optional object into your class under test.

You could use that to cover the first if statement: you expect the mock to see the isPresent() call, to return true, and to then return a specific string. Your testcase could then check "that expected string came back". Similar for the other way round, when the mocked Optional "is empty", then you ensure another string is returned, and you check for that.

But honestly, it is doubtful if you should do that all.

You should focus on the public contract that your method there provides.

And that would mean:

• Enable yourself that you can pass in a (real) Optional object into the class under test
• When your Optional is not empty, your test expects ... what you put into it
• When your Optional is empty, your test expects whatever extractText() will return

Of course, mocking is really problematic here: Optional is a final class. So you need to either use Mockito with "experimental support for final enabled", or you need to use PowerMock(ito) (which I strongly advise to never use).

So, as said: avoid mocking.

Answered By - GhostCat
Answer Checked By - Willingham (JavaFixing Volunteer)