This is my personalized solution to the Autobooks interview repository. To reiterate, the following requirements were mentioned:

• API listing all customers
• API retrieving a customer
• API adding a customer
• API updating a customer
• Unit tests
• Use .NET Core 3.1 or NET 5+

I did consider adding a delete endpoint, but since it was not explicitly specified, I did not do it.

• Upgraded to .NET 5.0
• Use generic Host instead of WebHost
• An API Controller implemented to serve the requirements listed for this assignment.
• Extensive unit and integration testing implemented
• Provided Postman collection that may be used to test the APIs after running dotnet watch run.

For unit testing, I am using:

• NUnit (for the unit test framework)
• NSubstitute (for mocking)
• AutoFixture (for easier "Arrange" in arrange-act-assert test structure)
• FluentAssertions (for more fluid and readable LINQ-style test assertions)

For general implementation in the main project:

• Autofac (my personal favorite DI container for implementing inversion of control)
• Newtsonsoft.Json (for JSON serialization)
• System.IO.Abstractions (for abstracting away the filesystem to greatly improve unit testing, since I can simulate file data without managing files in my tests)

For the foundation of the assignment, I'm using the following principles:

• CRUD for the API (minus the "D", of course!)
• Loosely follow the Unit of Work and Repository patterns for the persistence layer.

I chose to use UoW & Repo patterns with the main goals of:

• Anticipating that later we may want to replace JSON persistence with an actual database, such as with EFCore.
• Making unit testing easier since I can easily separate main business logic from the persistence concerns using a repository interface.

Repository pattern here doesn't show much value beyond this, especially since the data context only is concerned with one type of data: A list of customers. But long term, you'll be able to add more data points (such as a product listing in the grocery store) and you won't need to go back and touch existing code too much (I tried to keep things as SOLID as possible, namely open-closed in this case).

My test environment is Windows 10 x64 using Jetbrains Rider 2021.2. I only tested development mode using dotnet watch run, I did not do any publishing to IIS, etc.

Acceptance testing performed:

• Run all unit tests in Rider and verify they pass.
• Run all 4 requests in the provided Postman collection (GroceryStoreAPITests.postman_collection.json) and verify the results in the HTTP response as well as changes in the database.json file.
• Completely delete the database.json file and verify it is created on the next HTTP request.

Note: The GroceryStoreJsonDataContext uses relative paths to find and use database.json. In my tests, it was able to find this file without any additional changes to my project settings. If in your testing it is not able to find the file, please accept my apologies and try moving the database.json around to the appropriate location so that it may find the file.