public void playerKillsDeathCheck_Test()
{
Rulebook rulebook = new Rulebook();
Rulebook rb = rulebook;
rb.playerDeaths = 0;
rb.playerDeathCheck = 0;
rb.playerKillsDeathCounter = 20;
Assert.Throws <NullReferenceException>(() => rb.PlayerKillsDeathsCheck());
Assert.That(rb.playerKillsDeathCounter, Is.EqualTo(0));
}