Design Patterns: Asp.Net Core Web API, services, and repositories

Part 6: the NinjaController and the ninja sub-system

Posted by Carl-Hugo Marcotte on August 30, 2017

In the previous articles, we covered all the patterns needed to create a system where each responsibility is isolated. We implemented a Controller, a Service and a Repository. We also created unit and integration tests covering our specifications (as basic as they were). Our Clan sub-system is pretty basic indeed, but it allowed us to learn the patterns without bothering too much about external dependencies.

In this article we will define most of the ninja sub-system and implement the NinjaController while in the next articles, we will implement the service, the repository, talk about Azure Table Storage and the ForEvolve Framework.

Revisiting all the patterns in a more complex subsystem should help you learn them. Do not worry; I will also add a few more concepts along the way, this is not a copy/paste of my previous articles.

Skip the shared part

The series (shared section)

In the series, we will create an Asp.Net Core 2.0 Web API, and we will focus on the following major concerns:

The web part; the HTTP request and response handling.
The business logic; the domain.
The data access logic; reading and writing data.

During the article, I will try to include the thinking process behind the code.

Technology-wise, we will use Asp.Net Core, Azure Table Storage and ForEvolve Framework to build the Web API.

To use the ForEvolve Framework (or let’s say toolbox), you will need to install packages from a custom NuGet feed. If you dont know How to use a custom NuGet feed in Visual Studio 2017, feel free to take a look at this article. If you do, the ForEvolve NuGet feed URI is https://www.myget.org/F/forevolve/api/v3/index.json.

We will also use XUnit and Moq for both unit and integration testing.

Table of content

Article	Source code
Part 1: Introduction	1. NinjaApi - Starting point
Part 2: Dependency Injection	DependencyInjection sample
Part 3: Models and Controllers	3. NinjaApi - ClansControllers
Part 4: Services and the ClanService	4. NinjaApi - The ClanService
Part 5: Repositories, the ClanRepository, and integration testing	5. NinjaApi - Clans completed
Part 6: the NinjaController and the ninja sub-system	6. NinjaApi - NinjaController
Part 7: the NinjaService	7. NinjaApi - NinjaService
Part 8: Azure table storage and the data model	8. NinjaApi - NinjaEntity
Part 9: the NinjaMappingService and the Façade pattern	9. NinjaApi - NinjaMappingService
Part 10: the NinjaRepository and ForEvolve.Azure	10. NinjaApi - NinjaRepository
Part 11: Integration testing	11. NinjaApi - IntegrationTesting
More might come someday…

I will update the table of content as the series progress.

“Prerequisites”

In the series, I will cover multiple subjects, more or less in details, and I will assume that you have a little idea about what a Web API is, that you know C# and that you already have a development environment setup (i.e.: Visual Studio, Asp.Net Core, etc.).

The goal

At the end of this article series, you should be able to program an Asp.Net Core Web API in a structured and testable way using the explained techniques (design patterns). These design patterns offer a clean way to follow the Single Responsibility Principle.

Since design patterns are language-agnostic, you can use them in different applications and languages. In an Angular application, you will most likely use Dependency Injection for example.

This is one of the beauties of design patterns; they are tools to be used, not feared!

Asp.Net Core 2.0

At the time of the writing, Asp.Net Core 2.0 was still in prerelease, and I updated the code samples to use the release version.

You will need the .NET Core 2.0.0 SDK and Visual Studio 2017 update 3 or the IDE/code editor of your choosing.

Defining the interfaces

Now that we understand the patterns and know where we are heading, we will start by defining both our interfaces.

INinjaService

The ninja service should give us access to the Ninja objects. Once again, it will only support CRUD operations.

namespace ForEvolve.Blog.Samples.NinjaApi.Services
{
    public interface INinjaService
    {
        Task<IEnumerable<Ninja>> ReadAllAsync();
        Task<IEnumerable<Ninja>> ReadAllInClanAsync(string clanName);
        Task<Ninja> ReadOneAsync(string clanName, string ninjaKey);
        Task<Ninja> CreateAsync(Ninja ninja);
        Task<Ninja> UpdateAsync(Ninja ninja);
        Task<Ninja> DeleteAsync(string clanName, string ninjaKey);
    }
}

INinjaRepository

The INinjaRepository look the same as the INinjaService but their responsibilities are different. The repository’s goal is to read and write data while the service’s goal is to handle the domain logic.

As you can see, once again, we are building a simple CRUD data access interface.

namespace ForEvolve.Blog.Samples.NinjaApi.Repositories
{
    public interface INinjaRepository
    {
        Task<IEnumerable<Ninja>> ReadAllAsync();
        Task<IEnumerable<Ninja>> ReadAllInClanAsync(string clanName);
        Task<Ninja> ReadOneAsync(string clanName, string ninjaKey);
        Task<Ninja> CreateAsync(Ninja ninja);
        Task<Ninja> UpdateAsync(Ninja ninja);
        Task<Ninja> DeleteAsync(string clanName, string ninjaKey);
    }
}

Controller

Having our interfaces defined will allow us to create the NinjaController and unit test it.

As a reminder of the patterns, here is the schema from the first article of the series:

An HTTP request from the `Controller` to the data source, fully decoupled.

Creating the NinjaController

Once again, the NinjaController only exposes CRUD actions.

namespace ForEvolve.Blog.Samples.NinjaApi.Controllers
{
    [Route("v1/[controller]")]
    public class NinjaController : Controller
    {
        private readonly INinjaService _ninjaService;
        public NinjaController(INinjaService ninjaService)
        {
            _ninjaService = ninjaService ?? throw new ArgumentNullException(nameof(ninjaService));
        }

        [HttpGet]
        [ProducesResponseType(typeof(IEnumerable<Ninja>), StatusCodes.Status200OK)]
        public Task<IActionResult> ReadAllAsync()
        {
            throw new NotImplementedException();
        }

        [HttpGet("{clan}")]
        [ProducesResponseType(typeof(IEnumerable<Ninja>), StatusCodes.Status200OK)]
        [ProducesResponseType(StatusCodes.Status404NotFound)]
        public Task<IActionResult> ReadAllInClanAsync(string clan)
        {
            throw new NotImplementedException();
        }

        [HttpGet("{clan}/{key}")]
        [ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
        [ProducesResponseType(StatusCodes.Status404NotFound)]
        public Task<IActionResult> ReadOneAsync(string clan, string key)
        {
            throw new NotImplementedException();
        }

        [HttpPost]
        [ProducesResponseType(typeof(Ninja), StatusCodes.Status201Created)]
        [ProducesResponseType(StatusCodes.Status400BadRequest)]
        public Task<IActionResult> CreateAsync([FromBody]Ninja ninja)
        {
            throw new NotImplementedException();
        }

        [HttpPut]
        [ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
        [ProducesResponseType(StatusCodes.Status400BadRequest)]
        [ProducesResponseType(StatusCodes.Status404NotFound)]
        public Task<IActionResult> UpdateAsync([FromBody]Ninja value)
        {
            throw new NotImplementedException();
        }

        [HttpDelete("{clan}/{key}")]
        [ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
        [ProducesResponseType(StatusCodes.Status404NotFound)]
        public Task<IActionResult> DeleteAsync(string clan, string key)
        {
            throw new NotImplementedException();
        }
    }
}

ProducesResponseTypeAttribute

As you may have noticed, I decorated the controller actions with ProducesResponseType attributes. Since all actions are returning IActionResult, these attributes allowed me to define the real response type for each HTTP status code. For now, it is only useful for the humans programming the APIs, but we could auto-generate documentation of our APIs and even auto-generate REST clients.

See Swashbuckle.AspNetCore, which is a Swagger Spec generation tool, that includes an auto-generated UI. Swashbuckle will use the ProducesResponseTypeAttributes and turn them into Swagger Specifications for you.

Swagger is the world’s largest framework of API developer tools for the OpenAPI Specification(OAS), enabling development across the entire API lifecycle, from design and documentation, to test and deployment.

The definition is from the official Swagger home page.

More tooling

I never had the opportunity to use any of the following tools, but they both seem promising. They are on my "to try" list. That said, I will leave the links here for you to experiment and judge for yourself. When I get the opportunity to try them out, I will do my best to write about it.

AutoRest: generate a REST client automatically, based on Swagger specifications.
Refit: the automatic type-safe REST library for .NET Core, Xamarin and .NET
Please note that Refit has nothing to do with `ProducesResponseTypeAttribute`, but it seems like a great way of generating a REST client. So, while talking about it, I decided to include the links anyway.

Creating project specific exception classes

Before testing the controller, we will create some project specific exceptions.

Instead of using the built-in ones or returning null we will be able to throw and catch NinjaApiExceptions.

We will also create ClanNotFoundException and NinjaNotFoundException that inherits from NinjaApiException, as follow:

namespace ForEvolve.Blog.Samples.NinjaApi
{
    public class NinjaApiException : Exception
    {
        public NinjaApiException()
        {
        }

        public NinjaApiException(string message) : base(message)
        {
        }

        public NinjaApiException(string message, Exception innerException) : base(message, innerException)
        {
        }

        protected NinjaApiException(SerializationInfo info, StreamingContext context) : base(info, context)
        {
        }
    }

    public class ClanNotFoundException : NinjaApiException
    {
        public ClanNotFoundException(Clan clan)
            : this(clan.Name)
        {
        }

        public ClanNotFoundException(string clanName)
            : base($"Clan {clanName} was not found.")
        {
        }
    }

    public class NinjaNotFoundException : NinjaApiException
    {
        public NinjaNotFoundException(Ninja ninja)
            : base($"Ninja {ninja.Name} ({ninja.Key}) of clan {ninja.Clan.Name} was not found.")
        {
        }

        public NinjaNotFoundException(string clanName, string ninjaKey)
            : base($"Ninja {ninjaKey} of clan {clanName} was not found.")
        {
        }
    }
}

Why create NinjaApiException?

By having our exceptions inheriting from a project specific base exception, it is easier to differentiate the internal system exceptions from the external ones. For example, we could catch (NinjaApiException) to catch any of our application specific exceptions.

As for the other two, for example (with no knowledge of the system), reading catch (ClanNotFoundException) is easier to understand than reading catch (ArgumentException) or if (someObject == null).

Exceptions are a good way to propagates errors from one component of your system up to the user interface (the controller in our case).

Testing the NinjaController

The NinjaController already expect an INinjaService interface upon instantiation. The API contracts are also well defined, including different status code with ProducesResponseType attribute. Based on that, creating our unit tests should be relatively easy. We only have to translate our already well-thought use cases to XUnit test code.

namespace ForEvolve.Blog.Samples.NinjaApi.Controllers
{
    public class NinjaControllerTest
    {
        protected NinjaController ControllerUnderTest { get; }
        protected Mock<INinjaService> NinjaServiceMock { get; }

        public NinjaControllerTest()
        {
            NinjaServiceMock = new Mock<INinjaService>();
            ControllerUnderTest = new NinjaController(NinjaServiceMock.Object);
        }

        public class ReadAllAsync : NinjaControllerTest
        {
            [Fact]
            public async void Should_return_OkObjectResult_with_all_Ninja()
            {
                // Arrange
                var expectedNinjas = new Ninja[]
                {
                    new Ninja { Name = "Test Ninja 1" },
                    new Ninja { Name = "Test Ninja 2" },
                    new Ninja { Name = "Test Ninja 3" }
                };
                NinjaServiceMock
                    .Setup(x => x.ReadAllAsync())
                    .ReturnsAsync(expectedNinjas);

                // Act
                var result = await ControllerUnderTest.ReadAllAsync();

                // Assert
                var okResult = Assert.IsType<OkObjectResult>(result);
                Assert.Same(expectedNinjas, okResult.Value);
            }
        }

        public class ReadAllInClanAsync : NinjaControllerTest
        {
            [Fact]
            public async void Should_return_OkObjectResult_with_all_Ninja_in_Clan()
            {
                // Arrange
                var clanName = "Some clan name";
                var expectedNinjas = new Ninja[]
                {
                    new Ninja { Name = "Test Ninja 1" },
                    new Ninja { Name = "Test Ninja 2" },
                    new Ninja { Name = "Test Ninja 3" }
                };
                NinjaServiceMock
                    .Setup(x => x.ReadAllInClanAsync(clanName))
                    .ReturnsAsync(expectedNinjas);

                // Act
                var result = await ControllerUnderTest.ReadAllInClanAsync(clanName);

                // Assert
                var okResult = Assert.IsType<OkObjectResult>(result);
                Assert.Same(expectedNinjas, okResult.Value);
            }

            [Fact]
            public async void Should_return_NotFoundResult_when_ClanNotFoundException_is_thrown()
            {
                // Arrange
                var unexistingClanName = "Some clan name";
                NinjaServiceMock
                    .Setup(x => x.ReadAllInClanAsync(unexistingClanName))
                    .ThrowsAsync(new ClanNotFoundException(unexistingClanName));

                // Act
                var result = await ControllerUnderTest.ReadAllInClanAsync(unexistingClanName);

                // Assert
                Assert.IsType<NotFoundResult>(result);
            }
        }

        public class ReadOneAsync : NinjaControllerTest
        {
            [Fact]
            public async void Should_return_OkObjectResult_with_a_Ninja()
            {
                // Arrange
                var clanName = "Some clan name";
                var ninjaKey = "Some ninja key";
                var expectedNinja = new Ninja { Name = "Test Ninja 1" };
                NinjaServiceMock
                    .Setup(x => x.ReadOneAsync(clanName, ninjaKey))
                    .ReturnsAsync(expectedNinja);

                // Act
                var result = await ControllerUnderTest.ReadOneAsync(clanName, ninjaKey);

                // Assert
                var okResult = Assert.IsType<OkObjectResult>(result);
                Assert.Same(expectedNinja, okResult.Value);
            }

            [Fact]
            public async void Should_return_NotFoundResult_when_NinjaNotFoundException_is_thrown()
            {
                // Arrange
                var unexistingClanName = "Some clan name";
                var unexistingNinjaKey = "Some ninja key";
                NinjaServiceMock
                    .Setup(x => x.ReadOneAsync(unexistingClanName, unexistingNinjaKey))
                    .ThrowsAsync(new NinjaNotFoundException(unexistingClanName, unexistingNinjaKey));

                // Act
                var result = await ControllerUnderTest.ReadOneAsync(unexistingClanName, unexistingNinjaKey);

                // Assert
                Assert.IsType<NotFoundResult>(result);
            }
        }

        public class CreateAsync : NinjaControllerTest
        {
            [Fact]
            public async void Should_return_CreatedAtActionResult_with_the_created_Ninja()
            {
                // Arrange
                var expectedNinjaKey = "SomeNinjaKey";
                var expectedClanName = "My Clan";
                var expectedCreatedAtActionName = nameof(NinjaController.ReadOneAsync);
                var expectedNinja = new Ninja { Name = "Test Ninja 1", Clan = new Clan { Name = expectedClanName } };
                NinjaServiceMock
                    .Setup(x => x.CreateAsync(expectedNinja))
                    .ReturnsAsync(() =>
                    {
                        expectedNinja.Key = expectedNinjaKey;
                        return expectedNinja;
                    });

                // Act
                var result = await ControllerUnderTest.CreateAsync(expectedNinja);

                // Assert
                var createdResult = Assert.IsType<CreatedAtActionResult>(result);
                Assert.Same(expectedNinja, createdResult.Value);
                Assert.Equal(expectedCreatedAtActionName, createdResult.ActionName);
                Assert.Equal(
                    expectedNinjaKey,
                    createdResult.RouteValues.GetValueOrDefault("key")
                );
                Assert.Equal(
                    expectedClanName,
                    createdResult.RouteValues.GetValueOrDefault("clan")
                );
            }

            [Fact]
            public async void Should_return_BadRequestResult()
            {
                // Arrange
                var ninja = new Ninja { Name = "Test Ninja 1" };
                ControllerUnderTest.ModelState.AddModelError("Key", "Some error");

                // Act
                var result = await ControllerUnderTest.CreateAsync(ninja);

                // Assert
                var badRequestResult = Assert.IsType<BadRequestObjectResult>(result);
                Assert.IsType<SerializableError>(badRequestResult.Value);
            }
        }

        public class UpdateAsync : NinjaControllerTest
        {
            [Fact]
            public async void Should_return_OkObjectResult_with_the_updated_Ninja()
            {
                // Arrange
                var expectedNinja = new Ninja { Name = "Test Ninja 1" };
                NinjaServiceMock
                    .Setup(x => x.UpdateAsync(expectedNinja))
                    .ReturnsAsync(expectedNinja);

                // Act
                var result = await ControllerUnderTest.UpdateAsync(expectedNinja);

                // Assert
                var createdResult = Assert.IsType<OkObjectResult>(result);
                Assert.Same(expectedNinja, createdResult.Value);
            }

            [Fact]
            public async void Should_return_NotFoundResult_when_NinjaNotFoundException_is_thrown()
            {
                // Arrange
                var unexistingNinja = new Ninja { Name = "Test Ninja 1", Clan = new Clan { Name = "Some clan" } };
                NinjaServiceMock
                    .Setup(x => x.UpdateAsync(unexistingNinja))
                    .ThrowsAsync(new NinjaNotFoundException(unexistingNinja));

                // Act
                var result = await ControllerUnderTest.UpdateAsync(unexistingNinja);

                // Assert
                Assert.IsType<NotFoundResult>(result);
            }

            [Fact]
            public async void Should_return_BadRequestResult()
            {
                // Arrange
                var ninja = new Ninja { Name = "Test Ninja 1" };
                ControllerUnderTest.ModelState.AddModelError("Key", "Some error");

                // Act
                var result = await ControllerUnderTest.UpdateAsync(ninja);

                // Assert
                var badRequestResult = Assert.IsType<BadRequestObjectResult>(result);
                Assert.IsType<SerializableError>(badRequestResult.Value);
            }
        }

        public class DeleteAsync : NinjaControllerTest
        {
            [Fact]
            public async void Should_return_OkObjectResult_with_the_deleted_Ninja()
            {
                // Arrange
                var clanName = "My clan";
                var ninjaKey = "Some key";
                var expectedNinja = new Ninja { Name = "Test Ninja 1" };
                NinjaServiceMock
                    .Setup(x => x.DeleteAsync(clanName, ninjaKey))
                    .ReturnsAsync(expectedNinja);

                // Act
                var result = await ControllerUnderTest.DeleteAsync(clanName, ninjaKey);

                // Assert
                var createdResult = Assert.IsType<OkObjectResult>(result);
                Assert.Same(expectedNinja, createdResult.Value);
            }

            [Fact]
            public async void Should_return_NotFoundResult_when_NinjaNotFoundException_is_thrown()
            {
                // Arrange
                var unexistingClanName = "Some clan name";
                var unexistingNinjaKey = "Some ninja key";
                NinjaServiceMock
                    .Setup(x => x.DeleteAsync(unexistingClanName, unexistingNinjaKey))
                    .ThrowsAsync(new NinjaNotFoundException(unexistingClanName, unexistingNinjaKey));

                // Act
                var result = await ControllerUnderTest.DeleteAsync(unexistingClanName, unexistingNinjaKey);

                // Assert
                Assert.IsType<NotFoundResult>(result);
            }
        }
    }
}

Making the NinjaController tests pass

Now that we defined the expected behaviors of the NinjaController in our automated tests, it is time to make those tests pass.

In general, it should be pretty strait forward: delegates the business logic responsibility to the service class. Our controller will need to handle a few more things here for non-OK paths.

Let’s implement the NinjaController, method by method and test by test.

ReadAllAsync

The test says all: ReadAllAsync.Should_return_OkObjectResult_with_all_Ninja.

[HttpGet]
[ProducesResponseType(typeof(IEnumerable<Ninja>), StatusCodes.Status200OK)]
public async Task<IActionResult> ReadAllAsync()
{
    var allNinja = await _ninjaService.ReadAllAsync();
    return Ok(allNinja);
}

With those two lines of code, we are now down from 12 to 11 failing tests. This is a start!

ReadAllInClanAsync

For this one, we have two tests

ReadAllInClanAsync.Should_return_OkObjectResult_with_all_Ninja_in_Clan
ReadAllInClanAsync.Should_return_NotFoundResult_when_ClanNotFoundException_is_thrown

Should_return_OkObjectResult_with_all_Ninja_in_Clan

[HttpGet("{clan}")]
[ProducesResponseType(typeof(IEnumerable<Ninja>), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> ReadAllInClanAsync(string clan)
{
    var clanNinja = await _ninjaService.ReadAllInClanAsync(clan);
    return Ok(clanNinja);
}

Again, pretty straight forward. We are now down from 11 to 10 failing tests.

Should_return_NotFoundResult_when_ClanNotFoundException_is_thrown

[HttpGet("{clan}")]
[ProducesResponseType(typeof(IEnumerable<Ninja>), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> ReadAllInClanAsync(string clan)
{
    try
    {
        var clanNinja = await _ninjaService.ReadAllInClanAsync(clan);
        return Ok(clanNinja);
    }
    catch (ClanNotFoundException)
    {
        return NotFound();
    }
}

After this little update, we are down from 10 to 9 failing tests.

ReadOneAsync

For this one, we also have two tests

ReadOneAsync.Should_return_OkObjectResult_with_a_Ninja
ReadOneAsync.Should_return_NotFoundResult

Should_return_OkObjectResult_with_a_Ninja

[HttpGet("{clan}/{key}")]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> ReadOneAsync(string clan, string key)
{
    var ninja = await _ninjaService.ReadOneAsync(clan, key);
    return Ok(ninja);
}

Now down from 9 to 8 failing tests.

Should_return_NotFoundResult_when_NinjaNotFoundException_is_thrown

[HttpGet("{clan}/{key}")]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> ReadOneAsync(string clan, string key)
{
    try
    {
        var ninja = await _ninjaService.ReadOneAsync(clan, key);
        return Ok(ninja);
    }
    catch (NinjaNotFoundException)
    {
        return NotFound();
    }
}

Now down from 8 to 7 failing tests.

CreateAsync

CreateAsync also have two tests

CreateAsync.Should_return_CreatedAtActionResult_with_the_created_Ninja
CreateAsync.Should_return_BadRequestResult

Should_return_CreatedAtActionResult_with_the_created_Ninja

[HttpPost]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status201Created)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
public async Task<IActionResult> CreateAsync([FromBody]Ninja ninja)
{
    var createdNinja = await _ninjaService.CreateAsync(ninja);
    return CreatedAtAction(
        nameof(ReadOneAsync),
        new { clan = createdNinja.Clan.Name, key = createdNinja.Key },
        createdNinja
    );
}

This one is a little more “complex” since the CreatedAtAction (HTTP status code 201) must return the “read URL”. Now down from 7 to 6 failing tests.

Magic strings

As you may have noticed, I am using the nameof operator to avoid hard coding strings. In my opinion, strings should never be hard-coded anywhere in your code.

That said, out of the utopic world of endless money, time and workforce, it is tolerable to hard code your error messages (ex.: exceptions), test data (ex.: a dev database seeder), etc. Most of the time, you do not have an unlimited budget, and these will rarely change (creating a resource file ain’t that costly tho; just saying).

However, for code references (ex.: method name, class name, property name), DO NOT use a string, use the nameof operator.

In our last code block, nameof(ReadOneAsync) will simply become the string "ReadOneAsync", but, it is not a string until compiled. The nameof(...) operator is a constant expression. You could see this as a “dynamic constant”. Like a const, all references are replaced by the constant’s value at compile time. You can also use the nameof(...) operator anywhere you can use a constant, like in *Attribute or as a default parameter value.

One of the biggest advantages is that Visual Studio’s refactoring feature (renaming a method, a class, etc.) will also rename the nameof(...) references. More on that, if you use CodeLens or the “Find all references” on the ReadOneAsync method, Visual Studio will list nameof(...) as references.

If you do not know the nameof operator or want more info: nameof (C# Reference).

Should_return_BadRequestResult

[HttpPost]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status201Created)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
public async Task<IActionResult> CreateAsync([FromBody]Ninja ninja)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    var createdNinja = await _ninjaService.CreateAsync(ninja);
    return CreatedAtAction(
        nameof(ReadOneAsync),
        new { clan = createdNinja.Clan.Name, key = createdNinja.Key },
        createdNinja
    );
}

If there is a validation error, the API will return an HTTP status code 400 with the errors in its body. We do not have any restriction for the ninja (yet); our API is highly permissive right now. However, the controller does not have to know that, which would allow us to add validation later.

That said, we are now down from 6 to 5 failing tests. More than half done!

UpdateAsync

UpdateAsync has three tests:

One if everything is fine
One if the ninja’s validation fails
And the last one in case the ninja was not found

Should_return_OkObjectResult_with_the_updated_Ninja

[HttpPut]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> UpdateAsync([FromBody]Ninja ninja)
{
    var updatedNinja = await _ninjaService.UpdateAsync(ninja);
    return Ok(updatedNinja);
}

Down from 5 to 4 failing tests.

Should_return_NotFoundResult

[HttpPut]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> UpdateAsync([FromBody]Ninja ninja)
{
    try
    {
        var updatedNinja = await _ninjaService.UpdateAsync(ninja);
        return Ok(updatedNinja);
    }
    catch (NinjaNotFoundException)
    {
        return NotFound();
    }
}

Here we catch NinjaNotFoundException thrown by INinjaService in case the ninja to update does not exist. We will need to ensure this is implemented in NinjaService later.

Meanwhile, we are down from 4 to 3 failing tests.

Should_return_BadRequestResult

[HttpPut]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> UpdateAsync([FromBody]Ninja ninja)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    try
    {
        var updatedNinja = await _ninjaService.UpdateAsync(ninja);
        return Ok(updatedNinja);
    }
    catch (NinjaNotFoundException)
    {
        return NotFound();
    }
}

Down from 3 to 2 failing tests.

DeleteAsync

DeleteAsync has the last two tests needed to complete the NinjaController implementation.

Should_return_OkObjectResult_with_the_deleted_Ninja

[HttpDelete("{clan}/{key}")]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> DeleteAsync(string clan, string key)
{
    var deletedNinja = await _ninjaService.DeleteAsync(clan, key);
    return Ok(deletedNinja);
}

Down from 2 to 1 failing tests. Almost done!

Should_return_NotFoundResult

[HttpDelete("{clan}/{key}")]
[ProducesResponseType(typeof(Ninja), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> DeleteAsync(string clan, string key)
{
    try
    {
        var deletedNinja = await _ninjaService.DeleteAsync(clan, key);
        return Ok(deletedNinja);
    }
    catch (NinjaNotFoundException)
    {
        return NotFound();
    }
}

Bam! 29 passing tests! 0 failing test!

The end of this article

Running all tests gives us the green light to continue toward the service implementation, with 29 passing tests and no failing one.

What have we covered in this article?

In this article, we defined our ninja subsystem and implemented the NinjaController.

What’s next?

I originally planned to write a single article for both the NinjaController and the NinjaService. However, due to the quantity of code, it was becoming super long, so I decided to create two distinct part instead.

In the next article, we will implement the NinjaService and use our unit tests suite to do some refactoring.

Last word (shared section)

Table of content

Article	Source code
Part 1: Introduction	1. NinjaApi - Starting point
Part 2: Dependency Injection	DependencyInjection sample
Part 3: Models and Controllers	3. NinjaApi - ClansControllers
Part 4: Services and the ClanService	4. NinjaApi - The ClanService
Part 5: Repositories, the ClanRepository, and integration testing	5. NinjaApi - Clans completed
Part 6: the NinjaController and the ninja sub-system	6. NinjaApi - NinjaController
Part 7: the NinjaService	7. NinjaApi - NinjaService
Part 8: Azure table storage and the data model	8. NinjaApi - NinjaEntity
Part 9: the NinjaMappingService and the Façade pattern	9. NinjaApi - NinjaMappingService
Part 10: the NinjaRepository and ForEvolve.Azure	10. NinjaApi - NinjaRepository
Part 11: Integration testing	11. NinjaApi - IntegrationTesting
More might come someday…

Resources

Some additional resources used during the article (or not).

Articles & concepts

Tools & technologies

Code samples

Special thanks

I’d like to finish with special thanks to Emmanuel Genest who took the time to read my drafts and give me comments from a reader point of view.

The series (shared section)

Table of content

“Prerequisites”

The goal

Asp.Net Core 2.0

Defining the interfaces

INinjaService

INinjaRepository

Controller

Creating the NinjaController

Creating project specific exception classes

Testing the NinjaController

Making the NinjaController tests pass

ReadAllAsync

ReadAllInClanAsync

ReadOneAsync

CreateAsync

UpdateAsync

DeleteAsync

The end of this article

What have we covered in this article?

What’s next?

Last word (shared section)

Table of content

Resources

Articles & concepts

Tools & technologies

Code samples

Special thanks

Comments