Serializing test setups

[The-Futurist]

I'm relatively new to mocking (but not .Net) and its been a great help writing unit tests for a new asp.net web api.

As I've been refactoring I found myself wondering how to somehow automate the setup steps by using a setup json file.

For example I just finished this (it centralizes repetitive setup for mocked users for a bunch of unit tests)

        private void Setup_GetUserDataByOrgDefinedId(IDataRepository dataRepository, IEnumerable<UserData?> users, bool ReturnNull = false)
        {
            foreach (var user in users)
            {
                dataRepository.GetUserDataByOrgDefinedId(user.OrgDefinedId).Returns(ReturnNull ? (UserData?)null : user);
            }
        }

        private IEnumerable<UserData?> GenerateTestUsers()
        {
            yield return new() { FirstName = "Alice", LastName = "Smith",   UserId = 1111, OrgDefinedId = "111111111" };
            yield return new() { FirstName = "Steve", LastName = "Coogan",  UserId = 2222, OrgDefinedId = "222222222" };
            yield return new() { FirstName = "Mike",  LastName = "Jones",   UserId = 3333, OrgDefinedId = "333333333" };
            yield return new() { FirstName = "Ralph", LastName = "Edwards", UserId = 4444, OrgDefinedId = "444444444" };
        }

Where test can do:

            Setup_GetUserDataByOrgDefinedId(dataRepository, GenerateTestUsers());

So I was pondering would it be feasible to make this more generic, where I could specify say the interface IDataRepository and the specific method GetUserDataByOrgDefinedId in some general way in a config file, along with the data and the data type UserData? and so on?

On way that might be practical is to generate C# source from some form of JSON definition, that would be less painful that say doing it all with reflection and so on (which is of course possible but perhaps too much work).

I've done quite a lot of T4 template based code generation and had great success with that but was many years ago.

So has this ever come up before? has anyone done anything like it?

[Ergamon]

First I want to mention that this is probably the wrong place for this discussion, because software is usually defined in layers. NSubstitute is there for the purpose to create, well substitutes.

You can use anything you like on top of this. I usually work with AutoFixture.

So instead of
Substitute.For();

You configure autofixture and then call
fixture.Create();

After that the calls do not return what NSubstitute normally returns, but random data.

You could do similar things if you need more deterministic values. But as said, not really the purpose of NSub