@Test
public void setChild() throws Exception {

  assertEquals("A", expr.getChild(0).getText());
  assertEquals("0", expr.getChild(1).getText());
  expr.setChild(0, new VariableIdentifierExpr("B"));
  assertEquals("B", expr.getChild(0).getText());
  assertEquals("0", expr.getChild(1).getText());
  expr.setChild(1, new IntConstantExpr("3"));
  assertEquals("B", expr.getChild(0).getText());
  assertEquals("3", expr.getChild(1).getText());
}