How to write Unit Test for ASP.NET MVC?

Question

ASP.NET

There is a testable method:

public class CategoryModelService : ICategoryModelService
    {
        private readonly ICategoryModelRepository _categoryModelRepository;
        private readonly ICoastModelRepository _coastModelRepository;

        public CategoryModelService(ICategoryModelRepository _categoryModelRepository, ICoastModelRepository 
        _coastModelRepository)
        {
            this._categoryModelRepository = _categoryModelRepository;
            this._coastModelRepository = _coastModelRepository;
        }
        public async Task<CategoryModel> AddCategory(CategoryModel category)
        {
            var result = await _categoryModelRepository.AddCategory(category);  
            if (result != null)
            {
                return category;
            }
            else
            {
                return null;
            }
        }
}

And my test method which is to test the method from above:

[TestClass]
    public class CategoryModelServiceTest
    {
        [TestMethod]
        public void MyTest()
        {
            Mock<ICategoryModelRepository> _categoryModelRepository = new Mock<ICategoryModelRepository>();
            Mock<ICoastModelRepository> _coastModelRepository = new Mock<ICoastModelRepository>();

            CategoryModelService categoryModelService = new CategoryModelService(_categoryModelRepository.Object, _coastModelRepository.Object);

            CategoryModel model = new CategoryModel()
            {
                AutorCategoryId = ObjectId.GenerateNewId().ToString(),
                Id = ObjectId.GenerateNewId().ToString(),
                Income = false,
                Name = "Name",
                NetIncome = true
            };

            CategoryModel result = new CategoryModel();
            Task.Run(async () => { result = await categoryModelService.AddCategory(model); }).Wait();

            Assert.IsNotNull(result);
        }
    }

But, the result is always returned null.
Please tell me what needs to be changed in order to achieve the desired result

Answer 1

Mocks need to be configured. They return the default value of the required type by default. Thus, inside AddCategorythe mock repository, it always gives result == nulland, accordingly, nullreturns, the test falls.

var model = new CategoryModel { ... };

var categoryModelRepository = new Mock<ICategoryModelRepository>();

categoryModelRepository.Setup(x => x.AddCategory(model))
                                            .Returns(model);
// Или
categoryModelRepository.Setup(x => x.AddCategory( It.IsAny<CategoryModel>() ))
                                            .Returns(model);

// Act...

Assert.IsNotNull(result);