import core.thread : Thread;

auto sw = StopWatch(AutoStart.yes);
assert(sw.running);
Thread.sleep(usecs(1));
immutable t1 = sw.peek();
assert(t1 > Duration.zero);

sw.stop();
assert(!sw.running);
immutable t2 = sw.peek();
assert(t2 >= t1);
immutable t3 = sw.peek();
assert(t2 == t3);