How to convert to Xunit using mocking - xamarin.forms

Question

I have these two methods in my service class
public class PatientService : IPatientService
{
private readonly IRestClient _restClient;
private readonly IAppSettings _appSettings;
public PatientService(IRestClient restClient, IAppSettings appSettings)
{
_restClient = restClient;
_appSettings = appSettings;
}
public async Task<IList<PatientViewModel>> GetPatients(int wardId)
{
var url = _appSettings.Server + _appSettings.PatientServiceEndPoint + wardId;
var token = _appSettings.Token;
return GetPatientList(await _restClient.GetAsync<List<PatientInfo>>(url, token));
}
public IList<PatientViewModel> GetPatientList(IList<PatientInfo> patientInfoList)
{
return patientInfoList.Select(p => new PatientViewModel(p)).ToList();
}
}
I need to add this code to my Xunit.cs. How to do it?
I've implemented this and I do not know how to proceed.
private readonly PatientListPageViewModel _patientListPageViewModel;
private readonly Mock<IPatientService> _patient;
public PatientServiceTests()
{
_patient = new Mock<IPatientService>();
_patientListPageViewModel = new PatientListPageViewModel(_patient.Object);
}
[Fact]
public void GetListByWard_PassingWardId_GetPatientsCountAccordingToWardId()
{
}
This is what I tried to do. How to convert those two methods in service to be testable?

Answer 1

You did get mocking a bit wrong. It is not the component under test that is mocked, but its dependencies. When unit-testing you'd like to test a unit in isolation. Your case of mocking would be kind of correct if you unit-tested the PatientListPageViewModel, but since your test class is named PatientServiceTests I assume that you really wanted to test PatientService. If you wanted to test the former, you would be quite right to mock IPatientService, but when testing PatientService, IRestClient and IAppSettings shall be mocked
public PatientServiceTests()
{
_restClientMock = new Mock<IRestClient>();
_appSettingsMock = new Mock<IAppSettings>();
_patientService = new PatientService(_restClientMock.Object, _appSettingsMock.Object);
}
And your test could be something like
[Fact]
public async Task ReturnsCorrectPatientList() // async supported as of xUnit 1.9
{
// set up the mock
_restClientMock.SetUp(restClient => restClient.GetAsync<List<Patient>>(It.IsAny<string>(), It.IsAny<string>())
.Returns(() => Task.FromResult(/* what patients it shall return */));
var result = await _patientService.GetPatients(0);
// compare whether the returned result matches your expectations
}
If you wanted to test whether the URL is formed correctly, you could use Verify
[Theory]
[InlineData("SERVER", "ENDPOINT", 12, "1234", "SERVERENDPOINT12")]
[InlineData("https://localhost:65000", "/patients/", 5, https://localhost:65000/patients/5")]
public void TestWhetherCorrectUrlIsCalled(string server, string endpoint, int wardId, string token, string expectedUrl)
{
_appSettingsMock.SetupGet(appSettings => appSettings.Server).Returns(server);
_appSettingsMock.SetupGet(appSettings => appSettings.PatientServiceEndPoint).Returns(endpoint);
_appSettingsMock.SetupGet(appSettings => appSettings.Token).Returns(token);
_restClientMock.SetUp(restClient => restClient.GetAsync<List<Patient>>(It.IsAny<string>(), It.IsAny<string>())
.Returns(() => Task.FromResult(new List<Patient>()));
// we do not need the result
await _patientService.GetPatients(wardId);
_restClientMock.Verify(restClient => restClient.GetAsync<List<Patient>>(exptectedUrl, token), Times.Once);
}
We are setting up the IRestClient in this case, since it would return null otherwise. And await null would cause your test to fail. After GetPatients has been called we are using Verify to verify that GetAsync has been called with the correct parameters. If it has not been called, Verify will throw and your test will fail. Times.Once means, that GetAsync shall have been called once and only once.
On a side note: Viewmodels shall have a meaning in the context of your user interface only. Services shall be independent and hence not return viewmodels, as you did, but POCOs (or maybe domain models). In this case the interface of your service should be
public interface IPatientService
{
public async Task<IList<Patient>> GetPatients(int wardId);
// ...
}