测试一种从文件中读取和处理数据的方法

Question

我有以下代码：

public class FolderServiceImpl implements FolderService {
    private static final Logger L = LoggerFactory.getLogger(FolderServiceImpl.class);
    public int getStatus(String folderPath) {
        int status = 0;
        File folderStatusFile = new File(folderPath, ".folderstatus");
        if (folderStatusFile.exists()) {
            BufferedReader br = null;
            try {
                br = new BufferedReader(new FileReader(folderStatusFile));
                String line = br.readLine();
                status = Integer.parseInt(line);
            } catch (Exception e) {
                L.error("can't read file " + folderStatusFile.getAbsolutePath(), e);
                status = 4;
            } finally {
                if (br != null) {
                    try {
                        br.close();
                    } catch (IOException e) {
                        L.warn("could not close reader ", e);
                    }
                }
            }
        } else {
            status = 3;
        }
        return status;
    }
}

我想测试此方法，而无需为每种情况创建实际文件。我应该使用Java 1.7，Junit 4，Mockito和/或PowerMockito。

关于如何做的任何想法？

我正在谈论嘲笑数据源或简单地更改方法的输入。

我的测试看起来像这样：

`@rule public temeraryFolder文件夹= new temoraryFolder（）;

private FolderServiceImpl serviceToTest = new FolderServiceImpl();
private String folderPath;
@Before
public void setUp() {
    folderPath = folder.getRoot().getAbsolutePath();
    try {
        folder.newFile(".folderstatus");
    } catch (IOException e) {
        e.printStackTrace();
    }
}
@Test
public void shouldReturnFolderStatus3WhenFolderStatusIsNotFound() {
    // given
    deleteFolderStatusFile();
    // actual
    int status = serviceToTest.getFolderStatus(folderPath);
    // expected
    assertEquals(3, status);
}
@Test
public void shouldReturnFolderStatus4WhenTheStatusIsUnreadable() {
    // given
    writeStatusToTestFile("Test");
    // actual
    int status = serviceToTest.getFolderStatus(folderPath);
    // expected
    assertEquals(4, status);
}
@Test
public void shouldReturnFolderStatusInTheFile() {
    // given
    writeStatusToTestFile("1");
    // actual
    int status = serviceToTest.getFolderStatus(folderPath);
    // expected
    assertEquals(1, status);
}
private void writeStatusToTestFile(String status) {
    Path file = Paths.get(folder.getRoot().getAbsolutePath(), ".folderstatus");
    try {
        Files.write(file, status.getBytes());
    } catch (IOException e) {
        e.printStackTrace();
    }
}
private void deleteFolderStatusFile() {
    Path file = Paths.get(folder.getRoot().getAbsolutePath(), ".folderstatus");
    try {
        Files.delete(file);
    } catch (IOException e) {
        e.printStackTrace();
    }
}`

Answer 1

尽管@benheid的答案可能会更改为不同的方法。

IMHO每当我使用PowerMock（-ito）时，这都是不良设计的投降。此外，PowerMock解决方案将混淆测试覆盖工具，因为它在启动覆盖范围测量后更改了应用程序代码。

---

所以我宁愿使用的方法是坚持清洁代码和OOP规则。

其中之一是关注点的分离。

在您的情况下，该方法创建了一些基础架构类（依赖项），即FileReader和BufferedReader。

。

但是（直接）依赖关系的实例化不是包含业务逻辑的类的责任。

因此，我建议将代码重构为单独的类：

class ReaderFactory {
    public BufferedReader createFor(File file) throws FileNotFoundException {
        return new BufferedReader(new FileReader(file));
    }
}

您的班级会更改为：

class FolderServiceImpl {
    private static final Logger L = LoggerFactory.getLogger(FolderServiceImpl.class);
    private final ReaderFactory readerFactory;
    FolderServiceImpl(ReaderFactory readerFactory) {
        this.readerFactory = readerFactory;
    }
    public int getStatus(String folderPath) {
        int status = 0;
        File folderStatusFile = new File(folderPath, ".folderstatus");
        // try "with resource" takes care of closing the reader
        try (BufferedReader br = readerFactory.createFor(folderStatusFile);) {
            String line = br.readLine();
            status = Integer.parseInt(line);
        } catch (IOException e) {
            status = 3;
        } catch (Exception e) {
            L.error("can't read file " + folderStatusFile.getAbsolutePath(), e);
            status = 4;
        }
        return status;
    }
}

您的测试就是这样：

public class FolderServiceImplTest {
    private static final String ANY_FILE_NAME = "";
    @Rule
    public MockitoRule mockitoRule = MockitoJUnit.rule();
    @Rule
    public ExpectedException thrown = ExpectedException.none();
    @Mock
    private ReaderFactory readerFactory;
    @InjectMocks
    FolderServiceImpl sut;
    @Test
    public void getStatus_FileNotExisting_returnStatus3() throws Exception {
        // arrange
        Mockito.doThrow(new FileNotFoundException("UnitTest")).when(readerFactory).createFor(Mockito.any(File.class));
        // act
        int status = sut.getStatus(ANY_FILE_NAME);
        // assert
        Assert.assertThat("status",status,CoreMatchers.equalTo(3));
    }
    @Test
    public void getStatus_ValidFile_returnFileContentAsInt() throws Exception {
        // arrange
        BufferedReader bufferedReader = Mockito.mock(BufferedReader.class);
        Mockito.doReturn(bufferedReader).when(readerFactory).createFor(Mockito.any(File.class));
        Mockito.doReturn("4711").when(bufferedReader).readLine();
        // act
        int status = sut.getStatus(ANY_FILE_NAME);
        // assert
        Assert.assertThat("status",status,CoreMatchers.equalTo(4711));
    }
}

Answer 2

您必须使用类似的东西：

@RunWith(PowerMockRunner.class)
@PrepareForTest(tests.class)
public class test {
@Test
public void test() throws Exception {
    File fileMock = Mockito.mock(File.class);
    PowerMockito.whenNew(File.class).withArguments(Mockito.anyString(), Mockito.anyString()).thenReturn(fileMock);
    FolderServiceImpl sut = new FolderServiceImpl sut ();
    Mockito.when(fileMock.exists()).thenReturn(true);
    sut.getStatus("");
// Your verifications..
}
}

PowerMock将模拟在类的方法GetStatus中创建的文件对象。使用Mockito。当您可以说出代码中folderstusfile.exists（）的返回值时。

编辑

我已经在Maven中包括了以下两个罐子，但是您不需要使用maven：https：//mvnrepository.com/artifact/org.powermock/powermock/powermock-mock-module-junit4/1.4.6 and https：//https：//mvnrepository.com/artifact/org.powermock/powermock-api-mockito/1.4.9和https://mvnrepository.com/artifact/artifact/org.mockito/mockito/mockito-mockito-10.10.10.19