Unit testing

With unit tests you usually test individual service methods, by defining the outputs.

For unit tests we will use xUnit, NSubsitute and FluentAssertions. This is a personal prefference, you can use the libraries that fit best to your team

• create a new xUnit project inside the Tests folder in your started solution
• Call it:SpeakerService.Tests.Unit
• add a file named SpeakerServiceTests
• Install the NuGet packages: FluentAssertions, NSubstitute

Setting the ground

        private readonly ISpeakerRepository speakersRepository;
        private readonly ISpeakerService sut;
        private ILogger<Speaker.Service.SpeakerService> logger;
        private IMapper mapper;

        public SpeakerServiceTests()
        {
            this.speakersRepository = Substitute.For<ISpeakerRepository>(); ;
            logger = Substitute.For<ILogger<Speaker.Service.SpeakerService>>();

            if (mapper == null)
            {
                var mappingConfig = new MapperConfiguration(mc =>
                {
                    mc.AddProfile(new SpeakerMappingProfile());
                });
                IMapper mapper = mappingConfig.CreateMapper();
                this.mapper = mapper;
            }
            this.sut = new Speaker.Service.SpeakerService(logger, speakersRepository, mapper);
        }

• Create a folder named Helpers
• add a class named TestServerCallContext
• paste the code below

TestServerCallContext.cs

    public class TestServerCallContext : ServerCallContext
    {
        private readonly Metadata _requestHeaders;
        private readonly CancellationToken _cancellationToken;
        private readonly Metadata _responseTrailers;
        private readonly AuthContext _authContext;
        private readonly Dictionary<object, object> _userState;
        private WriteOptions? _writeOptions;

        public Metadata? ResponseHeaders { get; private set; }

        private TestServerCallContext(Metadata requestHeaders, CancellationToken cancellationToken)
        {
            _requestHeaders = requestHeaders;
            _cancellationToken = cancellationToken;
            _responseTrailers = new Metadata();
            _authContext = new AuthContext(string.Empty, new Dictionary<string, List<AuthProperty>>());
            _userState = new Dictionary<object, object>();
        }

        protected override string MethodCore => "MethodName";
        protected override string HostCore => "HostName";
        protected override string PeerCore => "PeerName";
        protected override DateTime DeadlineCore { get; }
        protected override Metadata RequestHeadersCore => _requestHeaders;
        protected override CancellationToken CancellationTokenCore => _cancellationToken;
        protected override Metadata ResponseTrailersCore => _responseTrailers;
        protected override Status StatusCore { get; set; }
        protected override WriteOptions? WriteOptionsCore { get => _writeOptions; set { _writeOptions = value; } }
        protected override AuthContext AuthContextCore => _authContext;

        protected override ContextPropagationToken CreatePropagationTokenCore(ContextPropagationOptions? options)
        {
            throw new NotImplementedException();
        }

        protected override Task WriteResponseHeadersAsyncCore(Metadata responseHeaders)
        {
            if (ResponseHeaders != null)
            {
                throw new InvalidOperationException("Response headers have already been written.");
            }

            ResponseHeaders = responseHeaders;
            return Task.CompletedTask;
        }

        protected override IDictionary<object, object> UserStateCore => _userState;

        public static TestServerCallContext Create(Metadata? requestHeaders = null, CancellationToken cancellationToken = default)
        {
            return new TestServerCallContext(requestHeaders ?? new Metadata(), cancellationToken);
        }
    }

This class will make

Then we need to test our first method - GetById.

Writing our first unit test

• add a method named GetById_ShouldReturn_an_Object

Method skeleton

       [Fact]
        public async Task GetById_ShouldReturn_an_Object()
        {

        }

• inside the class we will follow the AAA pattern as below

• Arrange( prepare the return objects, and make sure every line in the service will return what we need to cover the case)

Arrange

// Arrange
            var callContext = TestServerCallContext.Create();
            var request = new SpeakerFilterRequest { Id = 4 };


            var speaker = new Domain.Speaker()
            {
                Id = 4,
                City = "Oslo",
                Country = "Norway",
                Email = "[email protected]",
                FirstName = "Dev",
                LastName = "Speaker",
                Website = "www.speaker.com"
            };

            speakersRepository.GetByIdAsync(Arg.Any<int>())
               .Returns(speaker);

            var speakerResponse = new SpeakerResponse
            {
                Id = 4,
                City = "Bucharest",
                Country = "Belgium",
                Email = "[email protected]",
                FirstName = "Dev",
                LastName = "Speaker",
                Website = "www.speaker.com"
            };

• Act - call the actual service method that we want to test

 // Act
 var response = await sut.GetById(request, callContext);

• Assert what the expected result should be This section is where we use the (Expected result vs Actual result ) comparison

Assert

// Assert
response.Should().BeEquivalentTo(speakerResponse);

DON't open

Full implementation

public class SpeakerServiceTests
    {

        private readonly ISpeakerRepository speakersRepository;
        private readonly ISpeakerService sut;
        private ILogger<Speaker.Service.SpeakerService> logger;
        private IMapper mapper;

        public SpeakerServiceTests()
        {
            this.speakersRepository = Substitute.For<ISpeakerRepository>(); ;
            logger = Substitute.For<ILogger<Speaker.Service.SpeakerService>>();

            if (mapper == null)
            {
                var mappingConfig = new MapperConfiguration(mc =>
                {
                    mc.AddProfile(new SpeakerMappingProfile());
                });
                IMapper mapper = mappingConfig.CreateMapper();
                this.mapper = mapper;
            }
            this.sut = new Speaker.Service.SpeakerService(logger, speakersRepository, mapper);
        }

        [Fact]
        public async Task GetById_ShouldReturn_an_Object()
        {
            // Arrange
            var callContext = TestServerCallContext.Create();
            var request = new SpeakerFilterRequest { Id = 4 };


            var speaker = new Domain.Speaker()
            {
                Id = 4,
                City = "Bucharest",
                Country = "Belgium",
                Email = "[email protected]",
                FirstName = "Dev",
                LastName = "Speaker",
                Website = "www.speaker.com"
            };

            speakersRepository.GetByIdAsync(Arg.Any<int>())
               .Returns(speaker);

            var speakerResponse = new SpeakerResponse
            {
                Id = 4,
                City = "Bucharest",
                Country = "Belgium",
                Email = "[email protected]",
                FirstName = "Dev",
                LastName = "Speaker",
                Website = "www.speaker.com"
            };

            // Act
            var response = await sut.GetById(request, callContext);

            // Assert
            response.Should().BeEquivalentTo(speakerResponse);

        }

    }