### Question:
FileUtil { public static void copy (File source, File target) throws IOException { try (FileInputStream in = new FileInputStream(source); FileOutputStream out = new FileOutputStream(target)) { StreamUtil.copy(in, out); } }  static boolean renameTo(File source, File dest); static boolean deleteHarder(File file); static boolean deleteDirHarder(File file); static List<String> readLines(Reader in); static void unpackJar(ZipFile jar, File target, boolean cleanExistingDirs); static void unpackPacked200Jar(File packedJar, File target); static void copy(File source, File target); static void makeExecutable(File file); static void walkTree(File root, Visitor visitor);  }### Answer:
@Test public void shouldCopyFile () throws IOException { File source = _folder.newFile("source.txt"); File target = new File(_folder.getRoot(), "target.txt"); assertFalse(target.exists()); FileUtil.copy(source, target); assertTrue(target.exists()); }