java如何用easy mock模拟消费者链接？

Question

试图使用easy mock 3.3.1测试类Foo的方法foo，当链接两个以上的使用者时，它会引发空指针异常

   class Foo 
    {
      // init with constructor
       Bar1 bar1; 
       Bar2 bar2;
       Bar3 bar3;
       FooBar fooBar;
    
     public fooBar foo(){
        // line throwing NPE while running unit test.
        return fooBar.get(bar1.andThen(bar2).andThen(bar3));
      }
    }
    // Bar2 and Bar 3 has similar implementation
    class Bar1 extends Consumer<T> {
         @Override
         public void accept(T t) {...}
    }
    // class which accepts consumers.
    class FooBar {
      public fooBar get(Consumer consumer) {...}
    }
    // In test class, test method as such 
   {
      expect(fooBar.get(anyObject()).andReturn(MOCKED_OBJ);
      // if chaining only two object it works as expected. 
      // fooBar.get(bar1.andThen(bar2)) its returns MOCKED_OBJ but if chaining more than two its throws NPE
   }