public void Lockstep()
{
var dp1 = new DirectProcessor <int>();
var dp2 = new DirectProcessor <int>();
TestSubscriber <int> ts = dp1.Sample(dp2).Test();
ts.AssertEmpty();
dp1.OnNext(1);
dp1.OnNext(2);
dp2.OnNext(100);
ts.AssertValues(2);
dp2.OnNext(100);
ts.AssertValues(2);
dp1.OnNext(3);
dp1.OnNext(4);
dp2.OnNext(200);
ts.AssertValues(2, 4);
dp2.OnComplete();
ts.AssertResult(2, 4);
Assert.IsFalse(dp1.HasSubscribers);
Assert.IsFalse(dp2.HasSubscribers);
}