public sealed class RepositoryQuery<TEntity> : IRepositoryQuery<TEntity> where TEntity  : BaseEntity
   {

        private readonly List<Expression<Func<TEntity, object>>> _includeProperties;
        private readonly Repository<TEntity> _repository;
        private readonly List<Expression<Func<TEntity, bool>>> _filters;
        private Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> _orderByQuerable;
        private int? _page;
        private int? _pageSize;

        public RepositoryQuery(Repository<TEntity> repository)
        {
            _repository = repository;
            _includeProperties = new List<Expression<Func<TEntity, object>>>();
            _filters = new List<Expression<Func<TEntity, bool>>>();
        }

        public RepositoryQuery<TEntity> Filter(Expression<Func<TEntity, bool>> filter)
        {
            _filters.Add(filter);
            return this;
        }

        public RepositoryQuery<TEntity> OrderBy(Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy)
        {
            _orderByQuerable = orderBy;
            return this;
        }

        public RepositoryQuery<TEntity> Include(Expression<Func<TEntity, object>> expression)
        {
            _includeProperties.Add(expression);
            return this;
        }

        public IQueryable<TEntity> Get()
        {
            return _repository.Get(_filters, _orderByQuerable, _includeProperties, _page, _pageSize);
        }

    }

public class Repository<TEntity> : IRepository<TEntity> where TEntity : BaseEntity
    {
         private readonly Guid _instanceId;
        private readonly DbSet<TEntity> _dbSet;
        private readonly IDbContext _context;

        public Repository(IDbContext context)
        {
            _context = context;
            _dbSet = context.Set<TEntity>();
            _instanceId = Guid.NewGuid();
        }

        public virtual IRepositoryQuery<TEntity> Query()
        {
            var repositoryGetFluentHelper = new RepositoryQuery<TEntity>(this);
            return repositoryGetFluentHelper;
        }

        internal IQueryable<TEntity> Get(
            List<Expression<Func<TEntity, bool>>> filters = null,
            Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
            List<Expression<Func<TEntity, object>>> includeProperties = null,
            int? page = null,
            int? pageSize = null)
        {
            IQueryable<TEntity> query = _dbSet;

            if (includeProperties != null)
            {
                includeProperties.ForEach(i => query = query.Include(i));
            }

            if (filters != null && filters.Any())
            {
                query = filters.Aggregate(query, (current, filter) => current.Where(filter));
            }

            query = orderBy != null ? orderBy(query) : query.OrderBy(a => a.Id);

            if (page != null && pageSize != null)
            {
                query = query
                    .Skip((page.Value - 1)*pageSize.Value)
                    .Take(pageSize.Value);
            }
            return query;
        }


    }

var mockQuery = new Mock<IRepositoryQuery<TEntity>>();

// perform any setup needed on mockQuery for the particular System Under Test

var mockRepository = new Mock<IRepository<TEntity>>();

// perform any setup needed on mockRepository for the particular System Under Test

// component that relies on query and repository
// that is the System Under Test i.e. the focus of the unit test
var systemUnderTest = new SystemUnderTest(mockRepository.Object, mockQuery.Object);

var mock = new Mock<IRepositoryQuery<SomeClass>>();
mock.Setup(o => o.Get(/* test parameters */)).Returns(/* result */);

var myService = new SomeService(mock.Object);
Assert.That(myService.DoSomething(), Is.EqualTo(/* expected result*/));