Keep editor tooling from reacting to a test run

Editor tooling that reacts to domain reloads, asset imports or scene changes, such as a code generator, also reacts to what a test run does: the reloads it causes, the test scene it creates, the objects tests add. Have the tooling skip its work while tests run, by checking TestRun.IsActive.

[InitializeOnLoad]
internal static class MyGenerator
{
    static MyGenerator()
    {
        EditorApplication.hierarchyChanged += Regenerate;
    }

    private static void Regenerate()
    {
        if (TestRun.IsActive || EditorApplication.isPlayingOrWillChangePlaymode)
        {
            return;
        }
        // ...
    }
}

TestRun.IsActive is true from when a run reports its start until it reports its end, across the domain reloads in between, and for the whole of a batch-mode process started with -runTests. A Play Mode run reports its start only after the domain reload into Play Mode, so tooling that runs on that reload also checks EditorApplication.isPlayingOrWillChangePlaymode.

If your tooling's code is in an assembly definition, add Tsvrc.UdonTestKit to its references.