Mockito 使用then、thenAnswer 自定义方法处理逻辑

#Java Mockito 测试框架

then 和 thenAnswer 的效果是一样的。它们的参数是实现 Answer 接口的对象，在改对象中可以获取调用参数，自定义返回值。

示例：

import org.junit.Assert;
import org.junit.Test;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;

import static org.mockito.ArgumentMatchers.anyInt;
import static org.mockito.Mockito.when;

public class MockitoDemo {

    static class ExampleService {

        public int add(int a, int b) {
            return a+b;
        }

    }

    @Mock
    private ExampleService exampleService;

    @Test
    public void test() {

        MockitoAnnotations.initMocks(this);

        when(exampleService.add(anyInt(),anyInt())).thenAnswer(new Answer<Integer>() {
            @Override
            public Integer answer(InvocationOnMock invocation) throws Throwable {
                Object[] args = invocation.getArguments();
                // 获取参数
                Integer a = (Integer) args[0];
                Integer b = (Integer) args[1];

                // 根据第1个参数，返回不同的值
                if (a == 1) {
                    return 9;
                }
                if (a == 2) {
                    return 99;
                }
                if (a == 3) {
                    throw new RuntimeException("异常");
                }
                return 999;
            }
        });

        Assert.assertEquals(9, exampleService.add(1, 100));
        Assert.assertEquals(99, exampleService.add(2, 100));

        try {
            exampleService.add(3, 100);
            Assert.fail();
        } catch (RuntimeException ex) {
            Assert.assertEquals("异常", ex.getMessage());
        }
    }


}

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