Robolectric Resources$NotFoundException

I'm using robolectric to do unittest in my android project. My APPLICATION_ID is different from PackageName. So I follow the advice of the issues in robolectric github to make it work. Here is what I do.
First, I create a test runner

public class CustomRobolectricRunner extends RobolectricGradleTestRunner {

public CustomRobolectricRunner(Class<?> klass) throws InitializationError {
    super(klass);
}

protected AndroidManifest getAppManifest(Config config) {
    AndroidManifest appManifest = super.getAppManifest(config);
    FsFile androidManifestFile = appManifest.getAndroidManifestFile();
    String packageName = config.packageName();
    if (androidManifestFile.exists()) {
        return appManifest;
    } else {
        String moduleRoot = getModuleRootPath(config);
        androidManifestFile = FileFsFile.from(moduleRoot, appManifest.getAndroidManifestFile().getPath().replace("bundles", "manifests/full"));
        FsFile resDirectory = FileFsFile.from(moduleRoot, appManifest.getResDirectory().getPath().replace("/res", "").replace("bundles", "res/merged"));
        FsFile assetsDirectory = FileFsFile.from(moduleRoot, appManifest.getAssetsDirectory().getPath().replace("/assets", "").replace("bundles", "assets"));
        return new AndroidManifest(androidManifestFile, resDirectory, assetsDirectory);
    }
}

private String getModuleRootPath(Config config) {
    String moduleRoot = config.constants().getResource("").toString().replace("file:", "");
    return moduleRoot.substring(0, moduleRoot.indexOf("/build"));
}
}

Secondly, I create a config file, in test/resources. I set the packageName to my real packageName.

packageName=cn.campusapp.campus
sdk=21
shadows=ui.robolectric.ShadowMultiDex
constants=cn.campusapp.campus.BuildConfig
application = ui.TestApplication

But when i run the test. it report error as

android.content.res.Resources$NotFoundException: no such label cn.campusapp.forum:string/app_name
at org.robolectric.util.ActivityController.getActivityTitle(ActivityController.java:104)
at org.robolectric.util.ActivityController.attach(ActivityController.java:49)
at org.robolectric.util.ActivityController$1.run(ActivityController.java:121)
at org.robolectric.shadows.ShadowLooper.runPaused(ShadowLooper.java:304)
at org.robolectric.shadows.CoreShadowsAdapter$2.runPaused(CoreShadowsAdapter.java:45)
at org.robolectric.util.ActivityController.create(ActivityController.java:118)
at org.robolectric.util.ActivityController.create(ActivityController.java:129)
at org.robolectric.util.ActivityController.setup(ActivityController.java:210)
at org.robolectric.Robolectric.setupActivity(Robolectric.java:46)
at ui.VerifyActivityTest.testLogin(VerifyActivityTest.java:32)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.robolectric.RobolectricTestRunner$2.evaluate(RobolectricTestRunner.java:251)
at org.robolectric.RobolectricTestRunner.runChild(RobolectricTestRunner.java:188)
at org.robolectric.RobolectricTestRunner.runChild(RobolectricTestRunner.java:54)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.robolectric.RobolectricTestRunner$1.evaluate(RobolectricTestRunner.java:152)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:78)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:212)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:68)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)

Obviously, it's going to find the app_name string as the packageName-cn.campusapp.forum, which is my APPLICATION_ID. In other word, my config of packagename not work. I use the robolectric 3.0. Anybody can help me! Thanks.