Test a property that's populated with the FromServicesAttribute

Question

Question

We have a controller property that populates using the FromServicesAttribute.

[FromServices]
public IGenericRepository<TodoItem> TodoItemRepository { get; }

We want to test using this property. How do we mock it? For instance, if we were using constructor injection, we could pass the mock implementation to the constructor. How do we do this with a property this way?

Our Current Approach

This is how we're currently doing it with Moq.

[Fact]
public void GetAll_GetsCollection()
{
    // setup mock repository
    var all = new List<TodoItem>()
    {
        new TodoItem(),
        new TodoItem(),
        new TodoItem()
    };            

    var mockRepo = new Mock<IGenericRepository<TodoItem>>();
    mockRepo.Setup(x => x.All()).Returns(all);

    // setup mock unit of work
    // including what the [FromService] property will return
    var mockUnitOfWork = new Mock<IUnitOfWork>();
    mockUnitOfWork
        .Setup(x =>x.TodoItemRepository)
        .Returns(mockRepo.Object);

    // test controller
    TodoController controller = new TodoController(mockUnitOfWork.Object);
    var result = controller.GetAll();
    Assert.Equal(3, result.Count());
}

This does work and pass the tests. Maybe it's good enough. We're new to TDD.

Answer 1

Make the property settable (internal if needed) and use the InternalsVisibleTo to make the setter visible to the test assembly. Then, after you construct the object in the test code, set the property.

Or, if you use DI in your test code, create a fake IGenericRepository<TodoItem> and let the DI container inject it.