Q:

Unit test with Robolectric.buildAttributeSet() results in NullPointerException

I've got a PercentView class, and I'm trying to set up a test where I want to verify it was drawn to the correct size. I've got this working for a simple bar, but now I want an image/icon above it, which is a drawable (vector actually).
Some notes about this:

I have a drawable file (which is vector) that is named app_enabled.xml, which is main\res\drawable\app_enabled.xml.
I'm using Robolectric 3.5.1
I've seen the code for the test the Robolectric team has here: Robolectric example: ViewStubTest.java

I've declared the stylable:
<declare-styleable name="PercentageView">
    <attr name="image" format="integer" />
</declare-styleable>

And the view:
public class PercentageView extends View {
    private int _activeColor;
    private int _barBackgroundColor;
    private float _barHeight;
    private Drawable _icon;
    private Paint _barBackgroundPaint;
    private Paint _barActivePaint;
    private int _percent;

    public PercentageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        TypedArray args = context.getTheme().obtainStyledAttributes(
                attrs,
                R.styleable.PercentageView,
                0,
                0);

        try {
            _icon = args.getDrawable(R.styleable.PercentageView_image);

        } finally {
            args.recycle();
        }

        init();
    }
}

And now the test:
@RunWith(RobolectricTestRunner.class)
public class PercentageViewTests {
    private ShadowCanvas _shadowCanvas;
    private int _width;
    private int _height;
    private float _expectedPercentWidth;
    private int _thePercent;
    private Canvas _canvas;

    private PercentageView SetUpView(int width, int height, int percent, boolean useIcon) {
        ShadowApplication app = shadowOf(RuntimeEnvironment.application);

        //Attempt to pass in the icon, if useIcon is true
        AttributeSet attr = useIcon ? Robolectric.buildAttributeSet()
            .addAttribute(R.styleable.PercentageView_image, "@drawable/app_enabled") //NullPointerException here
            .build() : null;

        PercentageView view = new PercentageView(app.getApplicationContext(), attr);
        view.setLayoutParams(new ViewGroup.LayoutParams(width, height));
        view.setPercent(percent);

        return view;
    }

    @Before
    public void setup() {
        Random random = new Random(10);
        _width = random.nextInt(100);
        random.setSeed(101);
        _height = random.nextInt(200);

        random = new Random(0);
        _thePercent = random.nextInt(100);
        _expectedPercentWidth = _width * _thePercent / 100;

        _canvas = new Canvas();
        _shadowCanvas = shadowOf(_canvas);
    }

    @Test
    public void ShouldHaveIcon() {
        PercentageView view = SetUpView(_width, _height, _thePercent, true);
        view.onDraw(_canvas);

        assertThat(_shadowCanvas.getRectPaintHistoryCount(), is(equalTo(3)));
    }
}

And the VERY sad, stack trace:
java.lang.NullPointerException
at org.robolectric.Robolectric$AttributeSetBuilder.addAttribute(Robolectric.java:161)
at myorg.controls.PercentageViewTests.SetUpView(PercentageViewTests.java:41)
at myorg.controls.PercentageViewTests.ShouldHaveIcon(PercentageViewTests.java:140)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.robolectric.RobolectricTestRunner$HelperTestRunner$1.evaluate(RobolectricTestRunner.java:523)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.robolectric.internal.SandboxTestRunner$2.evaluate(SandboxTestRunner.java:226)
at org.robolectric.internal.SandboxTestRunner.runChild(SandboxTestRunner.java:108)
at org.robolectric.internal.SandboxTestRunner.runChild(SandboxTestRunner.java:35)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.robolectric.internal.SandboxTestRunner$1.evaluate(SandboxTestRunner.java:62)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMainV2.main(AppMainV2.java:131)

A:

Try replacing R.styleable.PercentageView_image with R.attr.image.
It seems the first argument to addAttribute() needs to be an attr res, rather than a stylable.

