private ImageIcon makeEmptyIcon(int w, int h, Color color) {
		BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
		if (color != null) {
			Graphics g = bi.getGraphics();
			g.setColor(color);
			g.fillRect(0, 0, w, h);
			g.dispose();
		}
		return new ImageIcon(bi);
	}
Minimal tests for MultiIconBuilder.  Doesn't test the produced images, just that it didn't cause an exception.
<p>
The showXYZ() methods are present so a human can run them as a test and see the output
Ghidra/Framework/Gui/src/test/java/resources/icons/MultiIconBuilderTest.java