[FIXED] Can I simulate a specific filesystem while unit testing?

Issue

I have been googling a little and did not find an answer which suited my specific case.

I am working on a project file manager classes, and discovered that it was developped to behave differently on Windows and Unix filesystems.

More specifically, it is compensating for the case-senstivity in Unix: when a file is not found, the manager will look for it in a case-insensitive way.

Before changing this code, I would like to implement some unit tests. However, our development machines and our CIP are both on Windows, and I have no Unix machine available. The machines and IDEs are provided by the customer. Virtualization is not an option, and dual-booting is even less.

Is there a way to test both Windows and Unix mode while being platform-independant for the build? I think the ideal would be to run the whole Test Class in a mode, and then in the other, but even a more hands-on solution would be great.

In production mode, the file managers are initialized using Spring, but they are the lowest level of the chain, using directly java.io.

Versions: Java 6, JUnit 4.9

Solution

You can use Jimfs with dependency

<dependency>
    <groupId>com.google.jimfs</groupId>
    <artifactId>jimfs</artifactId>
    <version>1.1</version>
</dependency>

Then you could create a linux, windows and Mac file systems using

 FileSystem fileSystem = Jimfs.newFileSystem(Configuration.osX());
 FileSystem fileSystem = Jimfs.newFileSystem(Configuration.windows());
 FileSystem fileSystem = Jimfs.newFileSystem(Configuration.unix());

example

class FilePathReader {

    String getSystemPath(Path path) {
        try {
            return path
              .toRealPath()
              .toString();
        } catch (IOException ex) {
            throw new UncheckedIOException(ex);
        }
    }
}

class FilePathReaderUnitTest {

    private static String DIRECTORY_NAME = "baeldung";

    private FilePathReader filePathReader = new FilePathReader();

    @Test
    @DisplayName("Should get path on windows")
    void givenWindowsSystem_shouldGetPath_thenReturnWindowsPath() throws Exception {
        FileSystem fileSystem = Jimfs.newFileSystem(Configuration.windows());
        Path path = getPathToFile(fileSystem);

        String stringPath = filePathReader.getSystemPath(path);

        assertEquals("C:\\work\\" + DIRECTORY_NAME, stringPath);
    }

    @Test
    @DisplayName("Should get path on unix")
    void givenUnixSystem_shouldGetPath_thenReturnUnixPath() throws Exception {
        FileSystem fileSystem = Jimfs.newFileSystem(Configuration.unix());
        Path path = getPathToFile(fileSystem);

        String stringPath = filePathReader.getSystemPath(path);

        assertEquals("/work/" + DIRECTORY_NAME, stringPath);
    }

    private Path getPathToFile(FileSystem fileSystem) throws Exception {
        Path path = fileSystem.getPath(DIRECTORY_NAME);
        Files.createDirectory(path);

        return path;
    }
}

All this copied from Baeldung.

Answered By - Tcheutchoua Steve
Answer Checked By - David Goodson (JavaFixing Volunteer)