Add your world's own test setup

When every test needs the same setup, such as your world's scene, a running session and the objects your tests look up, put it in a base class of your own that extends ClientSimTestBase, and extend that in your test classes.

public abstract class MyWorldTestBase : ClientSimTestBase
{
    protected Scoreboard Board;

    protected MyWorldTestBase() : base(TestScene.FromAsset("Assets/Scenes/MyWorld.unity"))
    {
    }

    [UnitySetUp]
    public IEnumerator StartWorld()
    {
        yield return Session.Start();
        Board = Object.FindObjectOfType<Scoreboard>();
    }
}

public class ScoreboardTests : MyWorldTestBase
{
    [UnityTest]
    public IEnumerator AddPoint_ForLocalPlayer_ShowsOnePoint()
    {
        Board.AddPoint();
        yield return null;

        Assert.That(Board.PointsOf(Networking.LocalPlayer), Is.EqualTo(1));
    }
}

Use NUnit attributes in your base class as you would in a test class. NUnit runs a base class's setup before yours and its teardown after yours, so with ClientSimTestBase underneath:

• your [UnitySetUp] and [SetUp] run with the test scene already loaded and active,
• your [TearDown] runs while the session is still running, and
• your [UnityTearDown] runs after ClientSim has ended, but before the test scene unloads.

ClientSimTestBase lists the full order.