assertFalse(c.next()); //the 'current' buffer doesn't enter the history
assertEquals("test", c.get());
assertFalse(c.prev());
assertEquals("test", c.get());
c.update("kkk");
c.commit();
assertEquals("test\nkkk\n", c.getAsDoc().get());
assertFalse(c.next());
assertEquals("", c.get());