Check the calls your code makes by name

UdonSharp code often calls another behaviour by method name, with SendCustomEvent, on a target and method name it stored earlier, such as a subscriber. Pass a CallbackSpy as that target, and check what its CallLog recorded.

Steps

1. Create a log with using var, so its spies are destroyed when the test ends, and create a spy:

   using var calls = new CallLog();
   CallbackSpy listener = calls.CreateSpy("Listener");

2. Give the spy to your code as the target, with one of its callbacks as the method name:

   scoreboard.Subscribe(listener, nameof(CallbackSpy.CallbackA));

3. Act, then assert on the calls, in order:

   scoreboard.AddPoint();
   
   Assert.That(calls, Is.EqualTo(new[] { "Listener.CallbackA" }));

Spies created from the same log record into it in the order the calls arrive, so one assertion covers several spies and the order between them. To ignore calls your setup caused, call calls.Clear() before acting.

Callbacks with your own names

When your code calls a fixed method name, such as OnRoundEnded, subclass CallbackSpy and call Record() from a method with that name:

public class RoundListenerSpy : CallbackSpy
{
    public void OnRoundEnded() => Record();
}

Create it with calls.CreateSpy<RoundListenerSpy>("Listener"), and it records "Listener.OnRoundEnded". Put the subclass in your Doubles assembly, so both Edit Mode and Play Mode tests can use it: Unity won't add a behaviour from the Edit Mode test assembly to a GameObject.

What to watch for

Outside Udon, as in a test, a call by name reaches only a public method with no parameters and exactly that name. A misspelled name does nothing and raises no error, so always assert on what the log recorded, not just that nothing failed.

SendCustomEventDelayedSeconds and SendCustomEventDelayedFrames never call anything outside Udon. When the code under test delays a call that way, call the delayed method directly from the test.