public void AddSkillBonus()
{
skill.AddBonus(42);
Assert.That(skill.Bonuses, Is.Not.Empty);
Assert.That(skill.Bonuses.Count, Is.EqualTo(1));
var bonus = skill.Bonuses.Single();
Assert.That(bonus.Value, Is.EqualTo(42));
Assert.That(bonus.Condition, Is.Empty);
Assert.That(skill.CircumstantialBonus, Is.False);
}