Junit Rule for working with temporary files and directories (draft)

TemporaryDirectory.java

import com.google.common.base.Charsets;
import com.google.common.io.Files;
import org.apache.commons.io.FileUtils;
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

import java.io.File;
import java.io.IOException;

/**
 * @author Kim A. Betti
 */
public class TemporaryDirectory implements TestRule {

    private volatile File dir;

    private TemporaryDirectory(File dir) {
        this.dir = dir;
    }

    public TemporaryDirectory() {
    }

    public File getDir() {
        return dir;
    }

    public TemporaryFile touch(String filename) throws IOException {
        File touched = new File(dir, filename);
        Files.touch(touched);

        return new TemporaryFile(touched);
    }

    public TemporaryDirectory mkdir(String name) {
        File subDirectory = new File(dir, name);
        if (subDirectory.mkdir()) {
            return new TemporaryDirectory(subDirectory);
        }
        else {
            throw new IllegalStateException("Unable to mkdir " + name);
        }
    }


    @Override
    public Statement apply(final Statement base, Description description) {
        return new Statement() {

            @Override
            public void evaluate() throws Throwable {
                try {
                    dir = Files.createTempDir();
                    base.evaluate();
                }
                finally {
                    FileUtils.deleteDirectory(dir);
                }
            }

        };
    }

    public static class TemporaryFile {

        private final File file;

        public TemporaryFile(File file) {
            this.file = file;
        }

        public void append(String line) throws IOException {
            Files.append(line, file, Charsets.UTF_8);
        }

        public File underlyingFile() {
            return file;
        }

    }

}