public void test() { MDependency10.AllInstances.generate = _ => 123; Class10 clazz = new Class10(); Assert.AreEqual(2 * 123, clazz.generate()); MDependency10.AllInstances.generate = null; Assert.AreEqual(2 * 999, clazz.generate()); MDependency10.AllInstances.generate = _ => 123; Assert.AreEqual(2 * 123, clazz.generate()); }