java - EasyMock + PowerMock:如何模拟字段？

让我们看一下这段代码：

    public class A {

        public void doSmth() {  // pay attention - void method
           // impl
        }
    }

    public class B {
       private A a_instance; // null

       public void doSmthElse() {
          a_instance.doSmth(); // NPE here without mock
          // also do smth. else
       }
    }

现在，我有B b = new B();，我想测试b.doSmthElse()，但是我需要先为a_instance对象创建一个模拟，否则我将得到NullPointerException！如何使用EasyMock或PowerMock实现此目标？

最佳答案

@Test
public void testDoSomething()
    {
    // setup: sut
    B b = new B();
    A mockA = EasyMock.createMock(A.class);
    b.setA_instance(mockA); // If you have a setter

    // setup: expectations
    mockA.doSmth();

    // exercise
    EasyMock.replay(mockA);
    b.doSmthElse();

    // verify
    EasyMock.verify(mockA);
    }

@Test
public void testDoSomething_setUsingReflection()
    {
    // setup: sut
    B b = new B();
    A mockA = EasyMock.createMock(A.class);
    // Set the collaborator using a Spring reflection utility
    ReflectionTestUtils.setField(b, "a_instance", mockA);

    // setup: expectations
    mockA.doSmth();

    // exercise
    EasyMock.replay(mockA);
    b.doSmthElse();

    // verify
    EasyMock.verify(mockA);
    }