!7

set flag NoHTML. // tt

p-exp {
  new NotifyingStringBuffer buf;
  final Var<Int> count = new(0);
  buf.onChange = ll(r { incIntVar(count) });
  
  assertEquals(0L, buf.changes);
  buf.append("yo");
  assertEquals(1L, buf.changes);
  buf.append(' ');
  buf.append("what");
  assertEquals(3L, buf.changes);
  assertEquals(3, count!);
  assertEqualsVerbose("yo what", str(buf));
  
  buf.setLength(2);
  assertEquals(4, count!);
  assertEqualsVerbose("yo", str(buf));
}