Creating Texture in headless LibGDX unit tests

Question

I am using the LibGDX headless backend to run jUnit tests. This works well for certain tests, but if I try to create a new Texture('myTexture.png');, I get a NullPointerException. The exact error is:

java.lang.NullPointerException
    at com.badlogic.gdx.graphics.GLTexture.createGLHandle(GLTexture.java:207)

To keep things simple, I created a method that does nothing other than load a texture:

public class TextureLoader {
    public Texture load(){
        return new Texture("badlogic.jpg");
    }
}

Then, my test class looks like this:

public class TextureTest {

    @Before
    public void before(){
        final HeadlessApplicationConfiguration config = new HeadlessApplicationConfiguration();
        new HeadlessApplication(new ApplicationListener() {
            // Override necessary methods
            ...
        }, config);
    }

    @Test
    public void shouldCreateTexture() {
        TextureLoader loader = new TextureLoader();
        assertNotNull( loader.load() );
    }
}

This method is working correctly in my actual app, just not in the unit tests.

How can I use the HeadlessApplication class to load Textures?

The libgdx Texture class basically wraps an OpenGL Texture handle. The headless backend has no OpenGL context (hence the "headless"). You can't create an OpenGL Texture handle without OpenGL context. — Xoppa, Sep 01 '14 at 21:08
Ok, that makes sense. I guess this is more of a general java question, but do you know of a good way to handle this in unit tests? Dependency injection could be used, but passing in every texture as a parameter sounds messy. — twiz, Sep 01 '14 at 21:57
For now, I've solved my problem by just using lwjgl instead of the headless backend. This seems counter-intuitive, since I assume unit testing is the main purpose for the existence of a headless backend. I understand that an actual headless openGL implementation would be pointless, but wouldn't it make sense for the headless backend to contain a mock version of the API to prevent exceptions? — twiz, Sep 02 '14 at 15:14
@twiz I totally agree with you. I'm currently facing this problem myself. Haven't entirely gotten it to work, could you add a self-answer to your question with your JUnit test code? — Simon Forsberg, Dec 21 '14 at 23:47

score 8 · Accepted Answer · edited Jul 19 '19 at 11:31

8

Mocking the Gdx.gl help me solved this NullPointerException during Texture creation:

import static org.mockito.Mockito.mock;

...

Gdx.gl = mock(GL20.class);

I used it with GdxTestRunner, see https://bitbucket.org/TomGrill/libgdx-testing-sample

public GdxTestRunner(Class<?> klass) throws InitializationError {
    super(klass);
    HeadlessApplicationConfiguration conf = new HeadlessApplicationConfiguration();
    new HeadlessApplication(this, conf);
    Gdx.gl = mock(GL20.class); // my improvement
}

edited Jul 19 '19 at 11:31

dStulle

609
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answered Dec 29 '14 at 09:36

Bill Lin

1,145
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I completely gave up on LibGDX and never actually tried this, but based on the upvotes, I'm going to accept the answer. – twiz Jul 19 '19 at 17:39

Creating Texture in headless LibGDX unit tests

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