java - 在使用 Mockito 测试时监视方法参数？

Question

假设我有一个类；

public class FooBar {

    public int getMethod(List<String> code){

        if(code.size() > 100)
            throw new Exception;

            return 0;
    }
}

我有一个这样的测试类；

@RunWith(PowerMockRunner.class)
@PrepareForTest(FooBar.class)
public class FooBarTest{

    FooBar fooBarInstance;

    @Before
    public void setUp() {

        //MockitoAnnotations.initMocks(this);
        fooBarInstance = new FooBar();   
    }

    @Test(expected = Exception.class)
    public void testGetCorrelationListCodesParameter() {

        List<String> codes = Mockito.spy(new ArrayList<String>());
        Mockito.doReturn(150).when(codes).size();
        fooBarInstance.getMethod(codes);
    }
}

如何让这个测试方法抛出异常？我已经处理了几个小时才能做到这一点。好吧，还是谢谢你。

Answer 1

不需要 spy ， mock 就足够了。正如@David 所说，也不需要也不建议对值对象进行模拟。

使用@Test(expected = Exception.class) 有很多缺点，当从意想不到的地方抛出异常时，测试可以通过。测试不工作，但显示为绿色。

我更喜欢使用 catch-exception 进行 BDD 风格测试.

Reasons for using catch-exceptions

(...) in comparison to the use of try/catch blocks.

• The test is more concise and easier to read.
• The test cannot be corrupted by a missing assertion. Assume you forgot to type fail() behind the method call that is expected to throw an exception.

(...) in comparison to test runner-specific mechanisms that catch and verify exceptions.

• A single test can verify more than one thrown exception.
• The test can verify the properties of the thrown exception after the exception is caught.
• The test can specify by which method call the exception must be thrown.
• The test does not depend on a specific test runner (JUnit4, TestNG).

import static com.googlecode.catchexception.CatchException.caughtException;
import static com.googlecode.catchexception.apis.CatchExceptionAssertJ.*;

public class FooBarTest {

    FooBar sut = new FooBar(); // System Under Test

    @Test
    public void shouldThrowExceptionWhenListHasTooManyElements() {

        when(sut).getMethod(listWithSize(150));

        then(caughtException()).isInstanceOf(Exception.class);
    }

    private List<String> listWithSize(int size) {
        return new ArrayList<String>(Arrays.asList(new String[size]));
    }
}

此测试的完整工作代码:https://gist.github.com/mariuszs/8543918

---

不推荐的解决方案，带有预期的和模拟。

@RunWith(MockitoJUnitRunner.class)
public class FooBarTest {

    @Mock
    List<String> codes;

    FooBar fooBarInstance = new FooBar();

    @Test(expected = Exception.class)
    public void shouldThrowExceptionWhenListHasTooManyElements() throws Exception {

        when(codes.size()).thenReturn(150);

        fooBarInstance.getMethod(codes);

    }
}