设置模拟无法正常工作（返回执行的存储库方法 null 值）

Question

I have some problem when I setup my mock for add entity. In case when I want get entity/entites my mock-setup is working fine, but when I want create(add). I setup method for create and it returned null in result.

PS AddProductAsync in my suspicion, this method may not work, although I checked in the debug, there is a call to the method

 public class ProductServiceTests
{
    private Mock<IProductRepository> _productMockRepo = new Mock<IProductRepository>();
    private ProductService _sut;

    public ProductServiceTests()
    {
        _sut = new ProductService(_productMockRepo.Object);
    }

It's my test method

[Fact]
    public async Task AddProduct_ShouldReturnProduct_WhenInputDataIsCorrect()
    {
        
        //Arrange
        var productId = Guid.NewGuid().ToString();
        var actualProduct = new ProductModel
        {
            Name = "test",
            Price = 1,
            Category = Category.Foods,
            Quantity = 2
        };
        
        var addingProduct = new Product
        {
            Name = actualProduct.Name,
            Price = actualProduct.Price,
            Category = actualProduct.Category,
            Quantity = actualProduct.Quantity
        };
        
        _productMockRepo.Setup(x => x.AddProductAsync(addingProduct))
            .ReturnsAsync(addingProduct);
        
        //Act
        var result = await _sut.AddProductAsync(actualProduct);
        
        //Assert
        
        Assert.Equal(actualProduct.Name, result.Name);
        _productMockRepo.Verify(x => x.AddProductAsync(addingProduct), Times.Once);
        

    }
}

_sut is my service and _productMockRepo is my mock repository

For testing I use NuGet packadge "Moq"

Thanks)

Answer 1

The issue is that the expectation was setup to use addingProduct , a specific instance

_productMockRepo.Setup(x => x.AddProductAsync(addingProduct))
        .ReturnsAsync(addingProduct);

but when exercising the test it is getting another instance created within the member under test

var result = await _sut.AddProductAsync(actualProduct);

which I can only assume does something similar to what was done in the here

var addingProduct = new Product {
    Name = actualProduct.Name,
    Price = actualProduct.Price,
    Category = actualProduct.Category,
    Quantity = actualProduct.Quantity
};

since the subject under test (ie: ProductService.AddProductAsync(Product product) ) is not shown.

Because it is not the actual instance used in the setup the mock will return null by default.

In this case, loosen the argument match during setup of expected behavior

//...

_productMockRepo
    .Setup(x => x.AddProductAsync(It.IsAny<Product>())) //<-- loosen expected match
    .ReturnsAsync((Product p) => p); //<-- return the argument that was passed to the member

//...

and change the expression for the verification to inspect what was passed

_productMockRepo.Verify(x => x.AddProductAsync(It.Is<Product>(p => addingProduct.Name == p.Name && ... )), Times.Once);

Reference: MOQ Quickstart - Matching Arguments