testing with mock objects

[Oliver Brocker]

Hello

I'm new to testing with mock objects and have an easy and maybe stupid question.

I have a handler class that among other things stores Groups in the database. The groups (and other data) are given in a data object.

For that handler I want write an unit test to check if groups are stored correct.

    /**
    * An easy version of the StorageHandler class.
    */
    class StorageHandler {
          
    /**
    * Stores given data into the database.
    * @param dataObj Contains all data to store.
    */
    public void saveData(Data dataObj){
     
    Set<Group> groups = dataObj.getGroups();
     
    for (Group group : groups) {
    saveGroup(group);
    }
    }
     
    private void saveGroup(Group group) {
    GroupDao daoGroup = (GroupDao) DaoManager.GetDao(GroupDao.class);
    daoGroup.save(group);
    }
    }

I found out that's good to use mock objects intead of using the database. So I decide to use EasyMock.

My problem is - in every code I found on the net EasyMock is used as follows:

    public class StorageHandlerTest {
    
    private StorageHandler storHandler;
    private GroupDao mock;
     
     
    @Before
    public void setUp() throws Exception {
    mock = EasyMock.createMock(Groupdao.class);
    storHandler.setGroupDao(mock);
    }
    }

So I have the problem that I don't provided that in my class. The StorageHandler's daos cannot set from the outside.

My question: Have I rewrite my class to use mock objects to set daos in that way? Or did I misunderstood the princip of using EasyMock?

Many thank for all help !
[ June 13, 2008: Message edited by: Oliver Brocker ]

[Jeanne Boyarsky]

Oliver,
Welcome to JavaRanch!

This is an English website? Can you post your question in English? While we do have a moderator who speaks German (that's what I think your post is written in, but I'm not sure), it wouldn't allow others to follow the conversation.

[Oliver Brocker]

I'm really sorry for wrote my first post in English! I worked from morning to night and I guess I was too tiered ...

For a clean view I now updated my first post.
[ June 13, 2008: Message edited by: Oliver Brocker ]

[Jeanne Boyarsky]

Oliver,
Yes. You often do need to make changes to a class to make it testable. The nice thing is after a while, that comes naturally and the code gets written in a testable way in the first place.

Common patterns are:
1) Initialize the variable in the constructor (to the value the "real" code will use) and provide a setter to inject the test value.
2) Provide a constructor taking the class to inject and optionally a default constructor which passes the value the real code will use to the new constructor.
3) Make the field to inject a package private field and set it directly.

I like options #1 and #2 much better, but have seen all three.

[Jeanne Boyarsky]

I changed the thread subject to English so people don't think they won't understand the thread.

[Oliver Brocker]

Thank you for your help! I have rewrite my classes now to try your first suggestion.

Do you know a good tutorial, ebook, book or code examples about testing daos with mock objects? I still have great difficulties by using JMock or Easymock and don't know where I can get more information.

So all examples I find on the net uses the old version of jMock (1.2.0). But for jMock 1.2.0 only a very simple documentation is availbale.
The documentation for jMock 2.40 is better but I didn't find any code example.

Typical problems of a beginner .

[Jeanne Boyarsky]

Oliver,
Thanks for updating the original post.

Book - "Test Driven" has a whole chapter on testing daos. It's an excellent book. The author happens to be a moderator here.

Which leads me to an article - this same author wrote an article on this same topic for our JavaRanch Journal. I'd start with that. If you like the article, the book is a good investment. It covers a lot of things that you will need to know about testing as you progress.

[Oliver Brocker]

Many thanks for the link and the book advice .