@Test
public void testSetDonutSize() throws Exception {

    Segment segment1 = spy(new Segment("s1", 25));
    Segment segment2 = spy(new Segment("s2", 25));
    Segment segment3 = spy(new Segment("s3", 25));
    Segment segment4 = spy(new Segment("s4", 25));
    SegmentFormatter formatter = spy(
            new SegmentFormatter(Color.GREEN, Color.GREEN, Color.GREEN, Color.GREEN));
    PieRenderer renderer = formatter.getRendererInstance(pieChart);
    pieChart.addSegment(segment1, formatter);
    pieChart.addSegment(segment2, formatter);
    pieChart.addSegment(segment3, formatter);
    pieChart.addSegment(segment4, formatter);
    renderer.setDonutSize(0.25f, PieRenderer.DonutMode.PERCENT);
    renderer.onRender(canvas, plotArea, segment1, formatter, renderStack);
    // TODO: verify radials are drown at the correct offsets from center
    //verify(canvas).drawLine(anyFloat(), anyFloat(), anyFloat(), anyFloat(), any(Paint.class));
}