@Test
public void testSetPersistentStorageDirectory() {

    Configuration c = new Configuration();
    c.setPersistentStorageDirectory(null);
    assertThat(Configuration.persistentStorageDirectory()).isEqualTo(System.getProperty("user.dir"));
    c = new Configuration();
    c.setPersistentStorageDirectory("");
    assertThat(Configuration.persistentStorageDirectory()).isEqualTo(System.getProperty("user.dir"));
}