无法通过Moq进行Cant设置模拟，以完成通用的无数任务

Question

I'm using the mocking library Moq and I'm unable to setup a mock for this signature:

Task<IEnumerable<TEntity>> GetAllAsync<TEntity>(
            Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
            string includeProperties = null,
            int? skip = null,
            int? take = null)
            where TEntity : class, IEntity;
}

Unit test class

using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading.Tasks;
using ICEBookshop.API.Factories;
using ICEBookshop.API.Interfaces;
using ICEBookshop.API.Models;
using Moq;
using SpecsFor;

namespace ICEBookshop.API.UnitTests.Factories
{
    public class GivenCreatingListOfProducts : SpecsFor<ProductFactory>
    {
        private Mock<IGenericRepository> _genericRepositorMock;

        protected override void Given()
        {
            _genericRepositorMock = new Mock<IGenericRepository>();
        }

        public class GivenRepositoryHasDataAndListOfProductsExist : GivenCreatingListOfProducts
        {
            protected override void Given()
            {
                _genericRepositorMock.Setup(
                        expr => expr.GetAllAsync<Product>(It.IsAny<Func<IQueryable<Product>>>(), null, null, null))
                    .ReturnsAsync<Product>(new List<Product>());

            }
        }
    }
}

This line of code is driving me crazy:

genericRepositorMock.Setup(
                        expr => expr.GetAllAsync<Product>(It.IsAny<Func<IQueryable<Product>>>(), null, null, null))
                    .ReturnsAsync<Product>(new List<Product>());

The problem is I don't know how to setup GetAllAsync so it will compile and that it will return a list of products. The desired behavior that it returns a list of products.

Can anyone help me with setting up the mock with this signature?

Answer 1

First, the initial example provided has the orderBy parameter as

Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy

But in the setup there is

It.IsAny<Func<IQueryable<Product>>>()

which wont match the definition of the interface and cause a compilation error.

Second, use It.IsAny<> for the optional parameters to allow the mocked method to be flexible when exercising the test.

The following simple example demonstrates

[TestMethod]
public async Task DummyTest() {
    //Arrange
    var mock = new Mock<IGenericRepository>();
    var expected = new List<Product>() { new Product() };
    mock.Setup(_ => _.GetAllAsync<Product>(
         It.IsAny<Func<IQueryable<Product>, IOrderedQueryable<Product>>>(),
         It.IsAny<string>(),
         It.IsAny<int?>(),
         It.IsAny<int?>()
        )).ReturnsAsync(expected);

    var repository = mock.Object;

    //Act
    var actual = await repository.GetAllAsync<Product>(); //<--optional parameters excluded

    //Assert
    CollectionAssert.AreEqual(expected, actual.ToList());
}