JUnit Tip: Use rules to manage temporary files and folders

You can remove the burden of deleting temporary files and folders from your test code by using a JUnit TemporaryFolder Rule. Rules themselves are new in JUnit 4.7 and are used to change the behavior of tests. For example, the following test creates and deletes a temporary file and folder:

package test;

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

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.TemporaryFolder;

public class TestTemporaryFolderRule {
    @Rule
    public TemporaryFolder testFolder = new TemporaryFolder();

    @Test
    public void testInTempFolder() throws IOException {
        File tempFile = testFolder.newFile("file.txt");
        File tempFolder = testFolder.newFolder("folder");
        System.out.println("Test folder: " + testFolder.getRoot());
        // test...
    }
}

In order to enable this feature, you must use the annotation @Rule on the declaration of the TemporaryFolder instance variable. The TemporaryFolder creates a folder in the default temporary file directory specified by the system property java.io.tmpdir. The method newFile creates a new file in the temporary directory and newFolder creates a new folder.

When the test method finishes, JUnit automatically deletes all files and directories in and including the TemporaryFolder. JUnit guarantees to delete the resources, whether the test passes or fails.