Files.write(ASCII, temp, UTF_8);
    assertThrows(IllegalArgumentException.class, () -> Files.copy(temp, temp));
    assertThat(Files.toString(temp, UTF_8)).isEqualTo(ASCII);
  }

  public void testCopyIdenticalFiles() throws IOException {
    File temp1 = createTempFile();
    Files.write(ASCII, temp1, UTF_8);
    File temp2 = createTempFile();
    Files.write(ASCII, temp2, UTF_8);
    Files.copy(temp1, temp2);