Parsing problem while testing API Services with Moq

Question

I'm trying to test my API with Moq but I'm having trouble with the mocked service and the execution of the test.

Unit test code:

public class UnitTest1
{
    private readonly INearEarthObjectService _repo;
    Mock<INearEarthObjectService> _mockRepo = new Mock<INearEarthObjectService>();
    public UnitTest1()
    {
        var services = new ServiceCollection();
        services.AddTransient<INearEarthObjectService, NearEarthObjectService>();
        services.AddTransient(sp => new HttpClient { BaseAddress = new Uri("https://api.nasa.gov/neo/rest/v1/") });

        var serviceProvider = services.BuildServiceProvider();

        _repo = serviceProvider.GetService<INearEarthObjectService>();
    }

    [Fact]
    public async void Test1()
    {
        _mockRepo.Setup(p => p.GetAllNeos(2)).Returns(Task.FromResult<IEnumerable<NearEarthObjectDTO>>).Verifiable();

        var result = _mockRepo.Object.GetAllNeos(2);

        Assert.True(result.IsCompletedSuccessfully);
    }
}

I'm having trouble in this line:

var result = _mockRepo.Object.GetAllNeos(2);

I gives me this exception:

System.ArgumentException: 'Object of type 'System.Int32' cannot be converted to type 'System.Collections.Generic.IEnumerable`1[NasaApi.Models.NearEarthObjectDTO]'.'

My Service code if it is useful:

public async Task<IEnumerable<NearEarthObjectDTO>> GetAllNeos(int days)
    {
        //Variable declaration
        HttpClient client = new HttpClient();
        DateTime today = DateTime.Now;
        DateTime nextday = today.AddDays(days);
        List<NearEarthObjectDTO> list = new List<NearEarthObjectDTO>();
        NearEarthObjectDTO neo;

        //URL parsing & data request
        var complete_url = url + start_date_param + today.Date.ToString(
            "yyyy-MM-dd") + "&" + end_date_param + nextday.Date.ToString("yyyy-MM-dd") + "&" + detailed_param + "&" + api_key_param;
        var feed = await client.GetFromJsonAsync<Rootobject>(complete_url);

        //Data filtering and parsing into DTO
        if (feed != null)
        {
            foreach (var register in feed.near_earth_objects)
            {
                foreach(var item in register.Value)
                {
                    neo = new NearEarthObjectDTO();
                    neo.Id = item.id;
                    neo.Nombre = item.name;
                    neo.Fecha = item.close_approach_data[0].close_approach_date;
                    neo.Velocidad = item.close_approach_data[0].relative_velocity.kilometers_per_hour;
                    neo.Diametro = DiameterCalc.Calc(item.estimated_diameter.meters.estimated_diameter_min,
                        item.estimated_diameter.meters.estimated_diameter_min);
                    neo.Planeta = item.close_approach_data[0].orbiting_body;

                    if (item.is_potentially_hazardous_asteroid && neo.Planeta.Equals("Earth") && !list.Contains(neo))
                    {
                        list.Add(neo);
                    }
                }
            }
        }

        //Return just the top 3 biggest potentially hazardous asteroids
        return list.OrderByDescending(x => x.Diametro).Take(3);
    }

I don't know where is the parsing problem because I'm a using a var which is supposed to adapt to any type.

Answer 1

You don't test the mock object. Your mock setup should be something like

_mockRepo.Setup(p => p.GetAllNeos(It.IsAny<int>)).ReturnsAsync(new List<NearEarthObjectDTO>()).Verifiable();

Here you are saying when GetAllNeos() gets called with any int it should return my List (which would be some fake data that the GetAllNeos() function is to return)