public void testMixingVolume {
  PigmentColor yellow = new PigmentColor(0, 50, 0);
  PigmentColor blue = new PigmentColor(0, 0, 50);
  
  StockPaint paint1 = new StockPaint(1.0, yellow);
  StockPaint paint2 = new StockPaint(1.5, blue);
  MixedPaint mix = new MixedPaint();

  mix.mixIn(paint1);
  mix.mixIn(paint2);
  assertEquals(2.5, mix.getVolume(), 0.01);
}
