public List<File> getOutdatedSearchDirectories() {
    return Collections.unmodifiableList(outdatedSearchDirectories);
  }
@Test
  public void getOutdatedSearchDirectories_returns_all_previously_used_es_data_directory_names() throws IOException {
    File sqHomeDir = temp.newFolder();
    File logDir = temp.newFolder();
    Props props = new Props(new Properties());
    props.set(PATH_DATA.getKey(), temp.newFolder().getAbsolutePath());
    props.set(PATH_HOME.getKey(), sqHomeDir.getAbsolutePath());
    props.set(PATH_TEMP.getKey(), temp.newFolder().getAbsolutePath());
    props.set(PATH_LOGS.getKey(), logDir.getAbsolutePath());

    EsInstallation underTest = new EsInstallation(props);

    assertThat(underTest.getOutdatedSearchDirectories())
      .extracting(File::getName)
      .containsExactlyInAnyOrder("es", "es5", "es6", "es7");
  }