Guice and JUnit

First of all: Do you use Guice as Dependency Injection Container in your Apps? If not, why?

Well, Guice is a lightweight dependency injection container made by Google, for Java 5 and above.

I will not explain much more about Guice in this post, maybe another day, in another post.

But, if you use Guice in your apps, you of course have doubts about how do I test this thing?, am I right?

Yep, I had these doubts too, then, most of time, I just made something like this:

public class FooTests {
  Injector i = Guice.createInjector(new FooModule());

  @Test
  public void testBar(){
    Bar b = i.getInstance(Bar.class);
    assertTrue(bar.thisShouldReturnTrue());
  }
}

Pretty easy, but, when you want to inject some generic thing, like Foo<Bar>, e.g., the things start to be ugly. So, you start look around, trying to find some framework… and found it, but these frameworks come with a lot of thing you don’t need, like Mockito or anything else. What could you do, so?

Well, I found a great way to solve this.

I’ll push it to Github soon, but, I can tell you that the use is pretty simple, and it only depends on JUnit 4.10. With my lib, you will do tests just like this:

@RunWith(GuiceTestRunner.class)
@GuiceModules(FooModule.class)
  public class FooTests {

  @Inject Bar bar;

  @Test
  public void testBar(){
    assertTrue(bar.thisShouldReturnTrue());
  }
}

I just didn’t make the push right now, because I’m using 3g, and, in Brazil, it’s damn slow and expensive, so, wait until tomorrow, please :)

Cheers.