FakeTimeProvider with auto advance enabled - should calling ToString() cause time to advance?

[egil]

I was looking over the code and noticed that ToString() calls GetUtcNow(). If AutoAdvanceAmount is greater than zero, then this would advance time whenever ToString is invoked.

In normal operations that is likely not going to cause problems, but if I understand how (visual) debuggers work correctly e.g. the ones in Visual Studio, if I am debugging my app and I am inspecting a FakeTimeProvider instance, VS will call ToString() causing the clock to advance. That is going to make debugging time-related issues pretty damn hard.

I think the fix is pretty simple:

-public override string ToString() => GetUtcNow().ToString("yyyy-MM-ddTHH:mm:ss.fff", CultureInfo.InvariantCulture);
+public override string ToString() => _now.ToString("yyyy-MM-ddTHH:mm:ss.fff", CultureInfo.InvariantCulture);

[sebastienros]

Would you mind submitting a PR with your suggestion, and a unit test that checks that?

[egil]

Sure, ill see what I can do. Was not able to get the build/tests running locally, but ill see what github CI can do for me. Off to bed. Ill check back in tomorrow.

[RussKie]

Was not able to get the build/tests running locally,

Have a look at our build guide - https://github.com/dotnet/extensions/blob/main/docs/building.md. Holler, if you have any specific issues, and we'll try to help.