不能模擬FileInputStream

Question

我有

@Component
public class CodesConverterService {    
private final FileInputStreamFactory fileInputStreamFactory;

public CodesConverterService(FileInputStreamFactory fileInputStreamFactory, YamlFactory yamlFactory) {
    this.fileInputStreamFactory = fileInputStreamFactory;

}
@EventListener(ApplicationReadyEvent.class)
    public void loadMappingsFromSource() {
        try {
            FileInputStream f = fileInputStreamFactory.getStream("mappingFile");
        } catch (Exception e) {
            throw new CodesConverterException("Can`t load mappings from source");
        }
    }

我的FileInputStreamFactory：

@Component
public class FileInputStreamFactory {

    public FileInputStream getStream(final String file) throws FileNotFoundException {
        return new FileInputStream(file);
    }
}

我的測試

@RunWith(SpringRunner.class)
public class CodesConverterServiceTest {

    @InjectMocks
    private CodesConverterService codesConverterService;

    @Mock
    private FileInputStreamFactory fileInputStreamFactory;

    @Mock
    private FileInputStream fileInputStream;
    @Test
    public void whenLoadMappingsFromSource_GoodPath() throws FileNotFoundException {
        when(fileInputStreamFactory.getStream("mappingFile")).thenReturn(fileInputStream);

        this.codesConverterService.loadMappingsFromSource();
    }

為什么我的f總是為null？ 我試過分配變化。 但它始終為空。 我已經為FileInputStream創建了工廠，因為我不想在測試中使用PowerMock模擬新FileInputStream上的創建。

Answer 1

我在下面的示例中重現了您的測試，該測試對我有用。
（已通過JUnit 4和Mockito 3.0.0和2.28.2 ）

我唯一更改的是Runner ，但根據您的評論，您已經這樣做了。

我刪除該示例中的注釋作為當測試與執行他們應該是不相關的MockitoJUnitRunner和改變的返回類型loadMappingsFromSource容易地添加Assert.assertNotNull 。 我還用RuntimeException替換了CodesConverterException 。

這些更改均不會影響測試本身。

即使僅存在帶有參數的構造函數，也可以正確創建FileInputStream的mock 。

@RunWith(MockitoJUnitRunner.class)
public class CodesConverterServiceTest {

    class YamlFactory {
    }

    class FileInputStreamFactory {
        public FileInputStream getStream(final String file) throws FileNotFoundException {
            return new FileInputStream(file);
        }
    }

    static class CodesConverterService {    

        private final FileInputStreamFactory fileInputStreamFactory;

        public CodesConverterService(FileInputStreamFactory fileInputStreamFactory, YamlFactory yamlFactory) {
            this.fileInputStreamFactory = fileInputStreamFactory;
        }

        public FileInputStream loadMappingsFromSource() {
            try {
                return fileInputStreamFactory.getStream("mappingFile");
            } catch (Exception e) {
                throw new RuntimeException("Can`t load mappings from source");
            }
        }
    }

    @InjectMocks
    private CodesConverterService codesConverterService;

    @Mock
    private FileInputStreamFactory fileInputStreamFactory;

    @Mock
    private FileInputStream fileInputStream;

    @Test
    public void whenLoadMappingsFromSource_GoodPath() throws FileNotFoundException {

        Mockito.when(fileInputStreamFactory.getStream("mappingFile")).thenReturn(fileInputStream);
        Assert.assertNotNull(codesConverterService.loadMappingsFromSource());
    }
}

Answer 2

1）嘗試以下代碼：

        @Test
        public void itShouldReturnFileInputStream() {
            FileInputStreamFactory mockFileInputStreamFactory = mock(FileInputStreamFactory.class);
            FileInputStream  mockFileInputStream = mock(FileInputStream.class);
            Mockito.doReturn(mockFileInputStream).when(mockFileInputStreamFactory).getStream("fileName");
            CodesConverterService  codeConverterService = new CodesConverterService(mockFileInputStreamFactory);
            assertThatCode(() -> codeConverterService.codeConverterService()).doesNotThrowAnyException();
        }

Answer 3

我弄清楚我在使用@RunWith(SpringRunner.class)和MockitoAnnotations.initMocks(this);是什么錯誤MockitoAnnotations.initMocks(this); 同時。 如果同時使用這兩種方法，則將創建怪人，但工作方式不正確。 所以我只是刪除了MockitoAnnotations.initMocks(this);

Answer 4

FileInputStream沒有no-arg構造函數。 這就是Mockito無法實例化模擬的原因。

您可以嘗試使其成為間諜，並相應地模擬所需的方法：

@Spy
private FileInputStream fileInputStreamSpy = new FileInputStream("dummy");

編輯 ：

另外，您可以通過以下方式在測試方法中創建模擬：

FileInputStream fileInputStreamMock = 
   Mockito.mock(FileInputStream.class, withSetting().useConstructor("dummy"));