模仿java.nio.files.class时出现NullPointer异常

Question

public class ClassToTest
{
    public List<String> walk(URI path)
    {
        List<String> directories= new List<String>();

        Path share = Paths.get(path);
        try
        {
            Stream<Path> folders = Files.list(share).filter(Files::isDirectory);
            folders.forEach(Path -> {
                {
                    directories.add(Path.toUri());
                }
            });

        }
        catch (IOException | SecurityException e)
        {
           System.out.println("Exception in crawling folder:"+path.toString());
           e.printStackTrace();
        }
        return directories;
    }
}

@RunWith(PowerMockRunner.class)
@PrepareForTest({Files.class, ClassToTest.class })
class ClassToTestUTest
{

    @Mock
    private Path folder1;
    @Mock
    private Path folder2;
    
    private ClassToTest underTest;
    @BeforeEach
    void setUp() throws Exception
    {
        PowerMockito.mockStatic(Files.class);
    }

    @Test
    void testWalk() throws IOException
    {
        String sharepath = "\\\\ip\\Share";
        Path temp = Paths.get(sharepath);
        
        Stream<Path> folders;
        ArrayList<Path> listOfFolders = new ArrayList<Path>();
        listOfFolders.add(folder1);
        listOfFolders.add(folder2);
        folders = listOfFolders.stream();
        
        when(Files.list(any())).thenReturn(folders);
        List<String> directories= underTest.walk(temp.toUri());
        
        //Check the directories list.
    }

}

java.lang.NullPointerException位于java.nio.file.files.provider（files.java:97)，位于java.nio.file.files.newDirectoryStream（files.java:457)，位于java.nio.file.files.list（files.java:3451)，位于com.classtotestStutest.TestWalk(ClasstotestStutest.java:51)

我发现了许多与嘲笑这个Files类有关的问题。我使用的是PowerMock 2.0.0、RC4和Mockito 2.23.4。

我哪里出错了？

Answer 1

面临着类似的问题。无法理解为什么java.nio.file.files模拟失败和其他final static方法被模拟。

class ClassUnderTest {
    
    public void methodUnderTest() throws IOException {
        //bla bla
        Files.lines(null/*some path*/);
        //bla bla
        return;
    }
}

将此更改为

class ClassUnderTest {
    
    public void methodUnderTest() throws IOException {
        //bla bla
        filesListWrapperMethod(null/*some path*/);
        //bla bla
        return;
    }
    
    @VisibleForTesting
    Stream<Path> filesListWrapperMethod(Path path) throws IOException {
        return Files.list(path);
    }

}

现在，您可以使用mockito.spy()并模拟特定的API。