Question

我想在CPU时间上对所有Java线程进行排序。我使用ThreadMXBean通过线程ID获取线程的CPU时间。比较器用于对线程ID进行分类。

public class ThreadStats{
    private static ThreadMXBean mxbean = ManagementFactory.getThreadMXBean();

    class ThreadCPUCompare implements Comparator<Long>{

        @Override
        public int compare(Long threadId1, Long threadId2) {
            return Long.compare(mxbean.getThreadCpuTime(threadId2), mxbean.getThreadCpuTime(threadId1));
        }
    }
}

我做了以下单元测试：

@RunWith(MockitoJUnitRunner.class)
public class ThreadStatsTest {

@InjectMocks ThreadCPUCompare comperator = new ThreadStats().new ThreadCPUCompare();
@Mock ThreadMXBean mxbean;

@Test
public void threadCPUSortTest() {
    Mockito.when(mxbean.getThreadCpuTime(1L)).thenReturn(3L);
    Mockito.when(mxbean.getThreadCpuTime(2L)).thenReturn(2L);
    Mockito.when(mxbean.getThreadCpuTime(3L)).thenReturn(4L);
    Mockito.when(mxbean.getThreadCpuTime(4L)).thenReturn(1L);

    List<Long>expectedList = new ArrayList<Long>();
    expectedList.add(3L);
    expectedList.add(1L);
    expectedList.add(2L);
    expectedList.add(4L);

    List<Long>actualList = new ArrayList<Long>();
    actualList.add(4L);
    actualList.add(2L);
    actualList.add(3L);
    actualList.add(1L);


    //Sorting of the actual list
    Collections.sort(actualList, comperator);

    assertEquals(expectedList, actualList);
    }
}

但是我无法让测试工作。我认为因为嘲弄不起作用。有人可以告诉我如何修理单元测试吗？

Answer 1

您的测试失败，因为没有注入模拟。 Mockito不会注入静态字段，也不会注入外部类（例如你的ThreadStats类）。

您需要编写如下代码：

class ThreadCPUCompare implements Comparator<Long>
{
    private ThreadMXBean mxbean;

    @Override
    public int compare(Long threadId1, Long threadId2) {
        return Long.compare(mxbean.getThreadCpuTime(threadId2), mxbean.getThreadCpuTime(threadId1));
    }
}

@RunWith(MockitoJUnitRunner.class)
public class ThreadStatsTest
{
    @Mock ThreadMXBean mxbean;
    @InjectMocks Comparator comperator = new ThreadCPUCompare();

    @Test
    public void threadCPUSortTest() {
        // do your tests exactly as before
    }
}

然后您将接受挑战，将其连接到生产代码中，但这是一个不同的练习，我会建议某种依赖注入（guice，spring，manual等，具体取决于上下文和首选项）。

Answer 2

编写测试的一种简单方法如下，不涉及模拟：

public class ThreadStatsTest {
    Comparator<Long> comparator = new ThreadStats().new ThreadCPUCompare();

    @Test
    public void orderThreadIdsFromLongestToShortestCPUTime() {
        long longLivedThread = Thread.currentThread().getId(); // > 0 cpu time
        long shortLivedThread = new Thread().getId(); // 0 cpu time

        int longTimeFirst = comparator.compare(longLivedThread, shortLivedThread);
        int sameTimes = comparator.compare(longLivedThread, longLivedThread);
        int longTimeSecond = comparator.compare(shortLivedThread, longLivedThread);

        assertEquals(-1, longTimeFirst);
        assertEquals( 0, sameTimes);
        assertEquals( 1, longTimeSecond);
    }
}

Java，单元测试模拟mxbean

2 个答案: