public async Task BasicTest()
{
var services = CreateServiceProviderFor <CounterService>();
var counters = services.GetRequiredService <CounterService>();
var c = Computed.GetExisting(() => counters.Get("a"));
c.Should().BeNull();
c = await Computed.Capture(_ => counters.Get("a"));
c.Value.Should().Be(0);
var c1 = Computed.GetExisting(() => counters.Get("a"));
c1.Should().BeSameAs(c);
await counters.Increment("a");
c.IsConsistent().Should().BeFalse();
c1 = Computed.GetExisting(() => counters.Get("a"));
c1.Should().BeNull();
}