Testing a private method in Java

Question

I am new writing good test cases, so please bear with me. Writing a test case for private methods

public Stock getStock(String stockTicker) {
            Stock company = new Stock();
            String url = getEndpointURL(stockTicker);
            htmlDocument = fetchHTMLDocument(url); // private method
            company.name = getStockName(); // private method uses htmlDocument
            company.actualPrice = getActualPrice(); // private method uses htmlDocument
            return company;
    }

Current Test case looks like

assertThat(selector.getActualPrice()).isGreaterThan(-1);
assertThat(selector.getStockName()).isNotNull();

But this doesn't allow me to make methods private..

To make the methods private, and since I want to test getStock only using public methods (like recommended in "How do you unit test private methods?"), I want to write test case for getStock method as below

Stock st = selector.getStock("AAPL");
assertThat(st.name).isNotNull();

i.e make assertions on Stock object

However, in this test, I want to avoid the backend call made by fetchHTML() and pass a custom Document to test the functioning of getStockName() and getActualPrice() method.

How do I do this without making methods public?

Do these methods use actually `htmlDocument`? it would be good if you could fix de example. Right now these methods look blind and totally opaque. On the other hand, does `fetchHTMLDocument` has any dependency you can mock/stubb? — Laiv, Sep 28 '17 at 14:28
The commonly-accepted "best practice" nowadays is to unit test your private methods *indirectly,* through the class's public API. — Robert Harvey, Sep 28 '17 at 16:44
@BobDalgleish: I took the freedom to edit the question a little bit, because it seems when one does not read it carefully, they can mistakenly believe it is a dupe, which it is not. — Doc Brown, Sep 28 '17 at 19:37
@RobertHarvey yes the other methods use `htmlDocument` and it is internal member of class stock selector — Incpetor, Sep 29 '17 at 04:55
The objective of a unit test is to verify the expected behaviour of the code via the contract, the implementation details should be immaterial, it should be possible to substitute an entirely different implementation, even a Mock. — Martin Spamer, Oct 19 '17 at 10:20

score 5 · Answer 1 · answered Sep 28 '17 at 16:22

I'm having a hard time understanding exactly what it is that you're asking but it seems like your question is more to do with removing the usage of an actual HTTP request than anything to do with private methods per se.

Instead of the fetchHTML function being a private function of that object, you should have a separate object that handles HTTP requests. You can then pass a mock version of this object into the constructor of the selector from tests, and this mock can return a fixed value instead of performing an actual HTTP request.

Testing a private method in Java

1 Answers1