Using multiple res folders with Robolectric

My current Gradle configuration has multiple (Merged) res folders:

sourceSets {
    androidTest {
        setRoot('src/test')
    }
    main {
        res.srcDirs =
            [
                'src/main/res/features/registration',
                'src/main/res/features/login',
                'src/main/res'
            ]
    }
}

But Robolectric allows me to configure a single directory using AndroidManifest:

public class RobolectricGradleTestRunner extends RobolectricTestRunner {
    private static final int MAX_SDK_SUPPORTED_BY_ROBOLECTRIC = 18;

    public RobolectricGradleTestRunner(Class<?> testClass) throws InitializationError {
        super(testClass);
    }

    @Override
    protected AndroidManifest getAppManifest(Config config) {
        String manifestProperty = "../app/src/main/AndroidManifest.xml";
        String resProperty = "../app/src/main/res";

        return new AndroidManifest(Fs.fileFromPath(manifestProperty), Fs.fileFromPath(resProperty)) {
            @Override
            public int getTargetSdkVersion() {
                return MAX_SDK_SUPPORTED_BY_ROBOLECTRIC;
            }
        };
    }
}

This way tests are failing. Is it possible to configure robolectric to reflect my gradle file?

Ok, this is the easiest way to do it, You will have to extend RobolectricTestRunner getAppManifest and createAppResourceLoader.

In getAppManifest you will simply have to store the manifest in a field, let's say mDefaultManifest.

In createAppResourceLoader you will have to add the right resources injected.

/**
 * TODO: Watch OUT this is copied from RobolectricTestRunner in Robolectric-2.4 keep it up to date!
 */
@Override
protected ResourceLoader createAppResourceLoader(ResourceLoader systemResourceLoader, AndroidManifest appManifest) {
    List<PackageResourceLoader> appAndLibraryResourceLoaders = new ArrayList<PackageResourceLoader>();
    for (ResourcePath resourcePath : appManifest.getIncludedResourcePaths()) {
        appAndLibraryResourceLoaders.add(createResourceLoader(resourcePath));
    }

        /* BEGIN EDIT */
        if(mDefaultManifest != null) {
            ResourcePath rpInjected = new ResourcePath(mDefaultManifest.getRClass(), mDefaultManifest.getPackageName(), Fs.fileFromPath("../app/src/main/res/features/registration"), mDefaultManifest.getAssetsDirectory());
            appAndLibraryResourceLoaders.add(createResourceLoader(rpInjected));
            rpInjected = new ResourcePath(mDefaultManifest.getRClass(), mDefaultManifest.getPackageName(), Fs.fileFromPath("../app/src/main/res/features/login"), mDefaultManifest.getAssetsDirectory());
            appAndLibraryResourceLoaders.add(createResourceLoader(rpInjected));
        }
        /* END EDIT */

    OverlayResourceLoader overlayResourceLoader = new OverlayResourceLoader(appManifest.getPackageName(), appAndLibraryResourceLoaders);

    Map<String, ResourceLoader> resourceLoaders = new HashMap<String, ResourceLoader>();
    resourceLoaders.put("android", systemResourceLoader);
    resourceLoaders.put(appManifest.getPackageName(), overlayResourceLoader);
    return new RoutingResourceLoader(resourceLoaders);
}

Do not forget to add @RunWith(YourTestRunner.class) in your test classes.