想要但不能调用:Mockito PrintWriter

嗨，我正在处理一个项目，并使用PrintWriter类打开和写入文件。但当我为其编写测试用例时，它在第153行出现以下错误

Wanted but not invoked:
  mockPrintWriter.println("ID    url1
  ");
 -> at x.y.z.verify(ProcessImageDataTest.java:153)
 Actually, there were zero interactions with this mock.

代码：(使用龙目图书馆(

ProcessImageData.java

@Setter
@RequiredArgsConstructor
public class ProcessImageData implements T {
    private final File newImageDataTextFile;
   @Override
    public void execute() {
       LineIterator inputFileIterator = null;
       try {
        File filteredImageDataTextFile = new File(filteredImageDataTextFilepath);
          PrintWriter writer = new PrintWriter(newImageDataTextFile);
          inputFileIterator = FileUtils.lineIterator(filteredImageDataTextFile, StandardCharsets.UTF_8.displayName());
          while (inputFileIterator.hasNext()) {
                    if(someCondition)
           **Line51**           writer.println(imageDataFileLine);
                    //FileUtils.writeStringToFile(newImageDataTextFile, imageDataFileLine + NEWLINE, true);
                }
            }          
      } catch (Exception e) {
      } finally {
          LineIterator.closeQuietly(inputFileIterator);
 **LINE63**         writer.close();
      }
  }

ProcessImageDataTest.java

@RunWith(PowerMockRunner.class)
@PrepareForTest({ ProcessImageData.class, FileUtils.class, Printwriter.class })
public class ProcessImageDataTest {
private ProcessImageData processImageData;
private static final String FILTERED_IMAGE_DATA_TEXT_FILE_PATH = "filteredFilepath";
private File FILTEREDFILE = new File(FILTERED_PATH);
private static final File IMAGE__FILE = new File("imageFilePath");
private LineIterator lineIterator;
@Mock
private PrintWriter mockPrintWriter;
@Before
public void init() throws Exception {
    MockitoAnnotations.initMocks(this);
    processImageData = new ProcessImageData(Palettes_file, FILTERED_PATH, IMAGE_FILE);
    PowerMockito.mockStatic(FileUtils.class);
    PowerMockito.whenNew(PrintWriter.class).withArguments(IMAGE_FILE).thenReturn(mockPrintWriter);
    PowerMockito.when(FileUtils.lineIterator(FILTERED_FILE, StandardCharsets.UTF_8.displayName())).thenReturn(lineIterator);
    PowerMockito.when(lineIterator.hasNext()).thenReturn(true, true, false);
}
@Test
public void testTaskWhenIDInDBAndStale() throws IOException {
    PowerMockito.when(lineIterator.nextLine()).thenReturn(ID2 + SPACE + URL1, ID1 + SPACE + URL2);
    processImageData.execute();
    List<String> exepctedFileContentOutput = Arrays.asList(ID2 + SPACE + URL1 + NEWLINE);
    verify(exepctedFileContentOutput, 1, 1);
}

@Test
public void testTaskWhenIDNotInDB() throws IOException {
    PowerMockito.when(lineIterator.nextLine()).thenReturn(ID2 + SPACE + URL1, ID3 + SPACE + URL2);
    processImageData.execute();
    List<String> exepctedFileContentOutput = Arrays.asList(ID3 + SPACE + URL2 + NEWLINE);
    verify(exepctedFileContentOutput, 1, 1);
}
private void verify(List<String> exepctedFileContentOutput, int fileWriteTimes, int fileReadTimes) throws IOException {
    for (String line : exepctedFileContentOutput){
**Line153**                     Mockito.verify(mockPrintWriter,  Mockito.times(fileWriteTimes)).print(line);  
    }
    PowerMockito.verifyStatic(Mockito.times(fileReadTimes));
    FileUtils.lineIterator(FILTERED_IMAGE_DATA_TEXT_FILE, StandardCharsets.UTF_8.displayName());
}
}

我还在嘲笑PrintWriter的一个新操作符，使用bean进行注入。我做错了什么？？我被它卡住了很长时间，却没有得到错误？感谢您的帮助。

更新：

我做了下面建议的更改并更新了代码，但现在我得到了错误：

Wanted but not invoked: mockPrintWriter.print("ASIN2 url1 "); -> 
at softlines.ctl.ruleExecutor.tasks.ProcessImageDataTest.verify‌(ProcessImageDataTes‌t.java:153) 
However, there were other interactions with this mock: -> at softlines.ctl.ruleExecutor.tasks.ProcessImageData.execute(Pr‌ocessImageData.java:‌51) ->  
at  softlines.ctl.ruleExecutor.tasks.ProcessImageData.execute(Pr‌ocessImageData.java:‌51) -> 
at softlines.ctl.ruleExecutor.tasks.ProcessImageData.execute(Pr‌ocessImageData.java:‌58) –

我在您的测试中看到3个问题：

您没有尝试模拟正确的构造函数，事实上，在方法execute中，您使用仅一个类型为File的参数创建PrintWriter，而使用两个类型为File和String的参数模拟<strong]构造函数>

所以代码应该是：

PowerMockito.whenNew(PrintWriter.class)
    .withArguments(IMAGE_FILE)
    .thenReturn(mockPrintWriter);

为了能够模拟构造函数，您需要准备创建实例的类，在本例中为ProcessImageData，因此需要在注释@PrepareForTest中添加ProcessImageData.class。(我不确定那里是否需要ProcessImageDataTest.class(
字段lineIterator应使用@Mock进行注释。
您不应该使用新行验证print，而应该直接验证println而不使用新行，这样就不太容易出错。

我简化了你的代码来展示这个想法。

假设ProcessImageData是：

public class ProcessImageData {
    private final File newImageDataTextFile;
    public ProcessImageData(final File newImageDataTextFile) {
        this.newImageDataTextFile = newImageDataTextFile;
    }
    public void execute() throws Exception{
        try (PrintWriter writer = new PrintWriter(newImageDataTextFile)) {
            LineIterator inputFileIterator = FileUtils.lineIterator(
                newImageDataTextFile, StandardCharsets.UTF_8.displayName()
             );
            while (inputFileIterator.hasNext()) {
                writer.println(inputFileIterator.nextLine());
            }
        }
    }
}

我的单元测试将是：

@RunWith(PowerMockRunner.class)
@PrepareForTest({ProcessImageData.class, FileUtils.class})
public class ProcessImageDataTest {
    private File file = new File("imageFilePath");
    private ProcessImageData processImageData;
    @Mock
    private PrintWriter mockPrintWriter;
    @Mock
    private LineIterator lineIterator;
    @Before
    public void init() throws Exception {
        MockitoAnnotations.initMocks(this);
        processImageData = new ProcessImageData(file);
        PowerMockito.whenNew(PrintWriter.class)
            .withArguments(file)
            .thenReturn(mockPrintWriter);
        PowerMockito.mockStatic(FileUtils.class);
        PowerMockito.when(
            FileUtils.lineIterator(file, StandardCharsets.UTF_8.displayName())
        ).thenReturn(lineIterator);
        PowerMockito.when(lineIterator.hasNext()).thenReturn(true, true, false);
    }
    @Test
    public void testExecute() throws Exception {
        PowerMockito.when(lineIterator.nextLine()).thenReturn("Foo", "Bar");
        processImageData.execute();
        Mockito.verify(mockPrintWriter,  Mockito.times(1)).println("Foo");
        Mockito.verify(mockPrintWriter,  Mockito.times(1)).println("Bar");
    }
}

有关更多详细信息，请参阅如何模拟新对象的构造。

如何在writer.close的单元测试中添加验证？

一种方法是简单地检查close()是否被调用一次，方法是在单元测试中添加下一行：

Mockito.verify(mockPrintWriter,  Mockito.times(1)).close();

PrintWriter的构造与mock不匹配。你告诉PowerMockito像这样返回你的模拟：

PowerMockito.whenNew(PrintWriter.class).withArguments(IMAGE_FILE , StandardCharsets.UTF_8.name()).thenReturn(mockPrintWriter);

所以你不得不说：

new PrintWriter(IMAGE_FILE, "UTF-8"); // 2 arguments

但是，在正在测试的代码中的execute方法中，您需要：

PrintWriter writer = new PrintWriter(newImageDataTextFile); // only 1 argument

因此，您要么需要更改PowerMockito withArguments子句，要么需要将"UTF-8"添加到execute方法中的构造函数调用中。

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