测试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;
    }
}

我想在不为每个案例创建实际文件的情况下测试此方法。我应该使用 Java 1.7、JUnit 4、Mockito and/or PowerMockito。

关于如何做到这一点有什么想法吗？

我说的是模拟数据源或简单地更改方法的输入。

我的测试看起来像这样：

`@规则 public TemporaryFolder 文件夹 = new TemporaryFolder();

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

你必须使用这样的东西：

@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 class 的 getStatus 方法中创建的文件对象。使用 Mockito.when，您可以在代码中说明 folderStatusFile.exists() 的 return 值是多少。

编辑

我在maven中包含了以下两个jar，但你不需要使用maven：https://mvnrepository.com/artifact/org.powermock/powermock-module-junit4/1.4.6 and https://mvnrepository.com/artifact/org.powermock/powermock-api-mockito/1.4.9 and https://mvnrepository.com/artifact/org.mockito/mockito-all/1.10.19

Answer 2

虽然@BenHeid 的回答可能有效，但我建议改用不同的方法。

恕我直言，每当我使用 PowerMock(-ito) 时，它都是对不良设计的投降。此外，PowerMock 解决方案会混淆测试覆盖率工具，因为它会在应用程序字节码被用于覆盖率测量后更改它。

所以我更喜欢的方法是坚持清洁代码 和 OOP 规则。

其中之一是关注点分离。

在您的情况下，该方法创建了一些基础设施 classes（依赖项）以供使用，即 FileReader 和 BufferedReader.

但是（直接）依赖项的实例化不是 class 包含业务逻辑的责任。

因此我建议将该代码重构为单独的 class:

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

您的 Class 将更改为：

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;
    }
}

你的测试是这样的：

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));
    }
}

测试从文件中读取和处理数据的方法

Testing a method that reads and processes data from a file

java

unit-testing

junit4

mockito