java - 通过 JUnit 模拟文件读/写

Question

如何通过 JUnit 模拟文件读取/写入？

这是我的场景

MyHandler.java

public abstract class MyHandler {

    private String path = //..path/to/file/here

    public synchronized void writeToFile(String infoText) {
        // Some processing
        // Writing to File Here
        File file = FileUtils.getFile(filepath);
        file.createNewFile();
        // file can't be written, throw FileWriteException
        if (file.canWrite()) {
            FileUtils.writeByteArrayToFile(file, infoText.getBytes(Charsets.UTF_8));
        } else {
            throw new FileWriteException();
        }
    }

    public String readFromFile() {
        // Reading from File here
        String infoText = "";
        File file = new File(path);
        // file can't be read, throw FileReadException
        if (file.canRead()) {
            infoText = FileUtils.readFileToString(file, Charsets.UTF_8);        
        } else {
            throw FileReadException();
        }

        return infoText
    }

}

MyHandlerTest.java

@RunWith(PowerMockRunner.class)
@PrepareForTest({
    MyHandler.class
})
public class MyHandlerTest {

    private static MyHandler handler = null;
    // Some Initialization for JUnit (i.e @Before, @BeforeClass, @After, etc)

    @Test(expected = FileWriteException.class)
    public void writeFileTest() throws Exception {

       handler.writeToFile("Test Write!");

    }

    @Test(expected = FileReadException.class)
    public void readFileTest() throws Exception {

       handler.readFromFile();

    }
}

鉴于上面的源代码，文件不可写(不允许写入权限)的场景是可以的，但是，当我尝试执行 file 不可读(不允许读取权限)的场景时。它总是读取文件，我已经尝试通过下面的测试代码修改文件权限

File f = new File("..path/to/file/here");
f.setReadable(false);

但是，我做了一些阅读，setReadable() 在 Windows 机器上运行时总是返回 false(失败)。

有没有办法以编程方式修改与 JUnit 相关的目标文件的文件权限？

注意

Target source code to test cannot be modified, meaning Myhandler.class is a legacy code which is not to be modified.

Answer 1

不依赖于操作系统文件权限，而是使用 PowerMock 模拟 FileUtils.getFile(...) 并使其返回一个 File 实例(例如匿名子类)，该实例返回 canWrite()/canRead 的特定值().

Mocking static methods with Mockito