The provider for the source IQueryable doesn’t implement IAsyncQueryProvider

I get stuck on this issue today and this lib resolve it for me https://github.com/romantitov/MockQueryable completely, please refer:

Mocking Entity Framework Core operations such ToListAsync, FirstOrDefaultAsync etc.

//1 - create a List<T> with test items
var users = new List<UserEntity>()
{
  new UserEntity{LastName = "ExistLastName", DateOfBirth = DateTime.Parse("01/20/2012")},
  ...
};

//2 - build mock by extension
var mock = users.AsQueryable().BuildMock();

//3 - setup the mock as Queryable for Moq
_userRepository.Setup(x => x.GetQueryable()).Returns(mock.Object);

//3 - setup the mock as Queryable for NSubstitute
_userRepository.GetQueryable().Returns(mock);