### Question:
Mask extends Band { public void setExpression(String expression) { this.initialExpression = expression; if(imageConfig != null && expression != null) getImageConfig().setValue(BandMathsType.PROPERTY_NAME_EXPRESSION, expression); } Mask(String name, int width, int height, ImageType imageType); ImageType getImageType(); final PropertyContainer getImageConfig(); Color getImageColor(); void setImageColor(Color color); double getImageTransparency(); void setImageTransparency(double transparency); void setExpression(String expression); @Override void acceptVisitor(ProductVisitor visitor); @Override void dispose(); @Override void updateExpression(final String oldExternalName, final String newExternalName); @Override Shape getValidShape();  }### Answer:
@Test public void testRenameBand() { Product product = new Product("t", "d", 1, 1); Band band = product.addBand("b", ProductData.TYPE_INT8); Mask mask = new Mask("m", 1, 1, Mask.BandMathsType.INSTANCE); mask.setExpression("b == 2"); product.getMaskGroup().add(mask); String expression = Mask.BandMathsType.getExpression(mask); assertEquals("b == 2", expression); band.setName("c"); expression = Mask.BandMathsType.getExpression(mask); assertEquals("c == 2", expression); }