mockito - 调用 when 方法时 powermock 出现 NullPointerException

Question

我似乎无法使用 powermock 模拟公共(public)函数调用的返回。

有人可以帮帮我吗？

失败的行是

PowerMockito.doReturn(aa).when(B.class, B.class.getDeclaredMethod("getA"));

特别是在“when”方法中

代码:

import static org.junit.Assert.fail;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
public class PowermockTest {

    private static class A {

        private int number;

        public A(int number) {
            this.number = number;
        }

        public int getNumber() {
            return number;
        }
    }

    private static class B {

        private int number;
        private A a;

        public B(int number) {
            this.number = number;
        }

        public A getA() {
            if (a == null) {
                a = new A(number);
            }
            return a;
        }
    }

    @Test
    public void testOdrService() {
        A aa = PowerMockito.mock(A.class);
        try {
            B bb = new B(3);
            PowerMockito.doReturn(aa).when(B.class, B.class.getDeclaredMethod("getA"));
        } catch (Exception e) {
            fail("Exception in test. " + e.getMessage());
        }
    }

}

附言:

将代码更改为以下工作但它强制创建我不想要的虚拟对象

B bb = new B(3);
B bb1 = PowerMockito.spy(bb);
PowerMockito.doReturn(aa).when(bb1).getA();
A mockedA = bb1.getA();

Answer 1

PowerMockito.doReturn(aa).when(B.class, B.class.getDeclaredMethod("getA"));

此语法专门用于 mocking static methods , 不是 mocking instance methods像 getA()。

在大多数情况下，您不需要保留原始( spy )对象。直接与 spy 互动:

B bb = PowerMockito.spy(new B(3));
// work with bb as normal
PowerMockito.doReturn(aa).when(bb).getA();
A mockedA = bb.getA(); // mockedA == aa