@Test
public void seriesToScreen_returnsScreenPoint() {

    when(xyPlot.getBounds()).thenReturn(new RectRegion(-100, 100, -100, 100));
    PointF point = graphWidget.seriesToScreen(new XYCoords(-100, 100));
    assertEquals(0f, point.x);
    assertEquals(0f, point.y);
    point = graphWidget.seriesToScreen(new XYCoords(100, -100));
    assertEquals(10f, point.x);
    assertEquals(100f, point.y);
    point = graphWidget.seriesToScreen(new XYCoords(0, 0));
    assertEquals(5f, point.x);
    assertEquals(50f, point.y);
}