Best way to automagically migrate tests from JUnit 3 to JUnit 4?

Question

I have a bunch of JUnit 3 classes which extend TestCase and would like to automatically migrate them to be JUnit4 tests with annotations such as @Before, @After, @Test, etc.
Any tool out there to do this in a big batch run?

Answer 1

I don't know of a tool that would do this at the moment - I'd expect Eclipse to provide some plugin fairly shortly - but you could knock up a simple source tree exploring Java class that would do it for you if you only want to do a basic conversion. I had to write something similar to automatically generate skeleton test cases for a legacy application so I've got a fair amount of the support code already. You're welcome to use it.

Answer 2

Not answering the question, but you do realize that you can run JUnit3 tests under JUnit4 without modification, yes?

Answer 3

There are, to my best knowledge, no available migration tools (yet). What I know is this:

• Last year, at OOPSLA in Nashville, was a paper about API migration but alas their tools seems not be openly available. I'll provide the link to the paper, (even though I dare it is of little use for you since it is rather theory heavy): "Annotation Refactoring: Inferring Upgrade Transformations for Legacy Applications".

• Above, I wrote "no available tool (yet)" because my student Lea Hänsenberger is currently working on an auotmated API migration from, not onyl, JUnit 4 a to JExample, but also from JUnit 3 to JUnit 4. Please follow JExample on Twitter to get notified when she releases a first beta.

I hope this information was of help for you.

Answer 4

In my opinion, it cannot be that hard. So let's try it:

@Test annotation

All methods beginning with public void test must precede the @Test annotation. This task is easy with a regex.

Get rid of extends TestCase

Remove exactly one occurence per file of the string

" extends TestCase"

SetUp and TearDown methods

Eclipse generates following setUp() method:

@Override
protected void setUp() throws Exception { }

Must be replaced by:

@Before
protected void setUp() throws Exception { }

Same for tearDown():

@Override
protected void tearDown() throws Exception { }

replaced by

@After
protected void tearDown() throws Exception { }

Imports

The imports has to be reorganized:

1. Remove import junit.framework.TestCase;
2. Add org.junit.*; or import org.junit.After; import org.junit.Before; import org.junit.Test;

Remove main methods?

Probably it's necessary to remove/refactor existing main methods that will execute the test.

Convert suite() method to @RunWithClass

According to saua's comment, there must be a conversion of the suite() method. Pattern will follow. Thanks, saua!

Conclusion

I think, it's done very easy via a set of regular expressions, even if it will kill my brain ;)

Answer 5

@Jeffery Fredrick

Using the old JUnit 3 classes with JUnit 4 without doing a full conversion causes other problems. For Example, the @BeforeClass was being ignored when I first converted to JUnit 4 and added the @BeforeClass annotation.

The story turns out to be is if JUnit 4 sees a subclass of junit.framework.TestCase it will run the tests in the old style, which means annotations like @BeforeClass get ignored.

Answer 6

Nice post. I did the upgrade using Netbeans with the following RegEx strings: (First line search-string, second one replace-string)

public void test
@Test\n    public void test

@Override\n.*protected void onSetUp
@Before\n    protected void onSetUp

@Override\n.*protected void onTearDown
@After\n    protected void onTearDown

Don't forget to flag the Regular Expression checkbox!