### Question:
ASTCustomOperator extends SimpleNode { public String getOperator() { return operator; } ASTCustomOperator(int id);  ASTCustomOperator(String operator);  ASTCustomOperator(String operator, Object[] nodes); @Override void jjtAddChild(Node n, int i); void setOperator(String operator); @Override void appendAsString(Appendable out); @Override int getType(); String getOperator(); @Override Expression shallowCopy();  }### Answer:
@Test public void testParse() { Expression exp = ExpressionFactory.exp("op('~~>', test, 'abc')"); assertTrue(exp instanceof ASTCustomOperator); assertEquals("~~>", ((ASTCustomOperator) exp).getOperator()); assertEquals("op(\"~~>\", test, \"abc\")", exp.toString()); }