Question
I am starting with Dapper, the micro-ORM, and i use the Dapper Rainbow. I want to test the queries and the data retrieved by them.
I mean, for example, i have the UserService with the method GetAll(), and i want to test that the sql query is retrieving all the users from some List (not from the database because i want the tests to be fast). Do you know how can i do that?
My service class (and the method i want to test):
public static class UserService{
public static IEnumerable<User> GetAll(){
return DB.Users.All();
}
}
Do you have any advice about unit testing queries and data retrieving?
Thanks
Popular Answer
I would suggest reading up on dependency injection and the repository pattern. If you take the approach that you have in the code above you will have a hard time mocking out the dependencies because the class and method is static.
Here is a better approach.
public interface IUserRepository
{
IEnumerable<User> GetAll()
}
public class UserRepository : IUserRepository
{
public IEnumerable<User> GetAll()
{
return DB.Users.All();
}
}
public class UserService
{
IUserRepository _userRepository;
public UserService(IUserRepository userRepository)
{
_userRepository = userRepository
}
public Enumerable<User> GetAll(){
return _userRepository.GetAll();
}
}
Now for testing you can mock out your repository. I use a mocking framework called NSubstitute which in my mind is a lot simpler than the others mentioned above, but that is a personal preference. To start with here is how you could write your test without any mocking framework.
public class FakeUserRepository : IUserRepository
{
public IEnumerable<User> GetAll()
{
return new List<User> { new User {FirstName='Bob', LastName='Smith'}, };
}
}
And in your test
[Test]
public void GetAll_ShouldReturnAllFromFake()
{
// Arrrange
var userService = new UserService(new FakeUserRepository())
// Act
var result = userService.GetAll();
// Assert
var user = result[0];
Assert.AreEqual("Bob", user.FirstName);
Assert.AreEqual("Smith", user.LastName);
}
This example is a little contrived as it doesn't really make sense to test that you can get data back from a fake repository. How you would use this in reality is if you had some business logic in your service that say got back a user and then check that they were older than a certain age or something. e.g. an IsLegalDrivingAge method on UserService.