@Test
public void testMkStringSeparator() {

    assertEquals("",      ACollectionHelper.mkString(Arrays.asList(),              "#"));
    assertEquals("a",     ACollectionHelper.mkString(Arrays.asList("a"),           "#"));
    assertEquals("a#b#c", ACollectionHelper.mkString(Arrays.asList("a", "b", "c"), "#"));
    assertEquals("",        ACollectionHelper.mkString(Arrays.asList(),              "?!"));
    assertEquals("a",       ACollectionHelper.mkString(Arrays.asList("a"),           "?!"));
    assertEquals("a?!b?!c", ACollectionHelper.mkString(Arrays.asList("a", "b", "c"), "?!"));
}