part of medium class, look at https://gist.github.com/cyberhck/e142b7b94fd939691f67a6d3342094b1 for all classes

BadClass.test.cs

namespace Tests
{
    public class BadClassTest
    {
        [Test]
        public void TestGreetDoesNotThrowException()
        {
            var unit = new BadClass();
            // var mock = new Mock<IService>(); (setup as well)
            // use reflection to change the implementation under the hood, (unit._service = mock)
            Assert.DoesNotThrow(() => unit.Greet())
        }
    }
}