Any developer that you speak to, will tell you the importance of unit testing, not only its a check against your logic, but it also avoids bugs and helps you to have confidence in your work that goes into production.
I love Microsoft.Extensions.DependencyInjection a.k.a Built in DI in .NET core. Although it lacks some of the advance configurations supported by other DI frameworks like Autofac, the reason it wins me over every time is the simplicity
All .Net core app types in have a DI starting point or anchor point i.e startup.cs except console application. Here is a short guide to setup DI in a .NET Core console app. Let's create a simple console