java - 无法模拟 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");
        }
    }

我的文件输入流工厂:

@Component
public class FileInputStreamFactory {

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

我的测试

@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();
    }

为什么我的 f 总是 null？我尝试过很多变化。但它始终为空。我为 FileInputStream 创建了工厂，因为我不想在测试中使用 PowerMock 来模拟新 FileInputStream 的创建。

Answer 1

我在下面的示例中重现了您的测试，这对我有用。
(使用 JUnit 4 和 Mockito 3.0.0 和 2.28.2 进行验证)

我唯一改变的是Runner，但根据您的评论，您已经这样做了。

我删除了示例中的注释，因为当使用 MockitoJUnitRunner 执行测试时它们应该是不相关的，并更改了 loadMappingsFromSource 的返回类型以轻松添加该 Assert.assertNotNull。我还用 RuntimeException 替换了 CodesConverterException。

这些更改都不会影响测试本身。

即使只有带有参数的构造函数，FileInputStream 的 mock 也已正确创建。

@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());
    }
}