Trying Clean Architecture on Golang

Independent, Testable , and Clean

Iman Tumorang
Jul 7, 2017 · 6 min read

After reading the uncle Bob’s Clean Architecture Concept, I’m trying to implement it in Golang. This is a similar architecture that we used in our company, Kurio - App Berita Indonesia, but a little different structure. Not too different, same concept but different in folder structure.

You can look for a sample project here https://github.com/bxcodec/go-clean-arch, a sample CRUD management article.

Image for post
Image for post
  • Disclaimer :
    I’m not recommending any library or framework used here. You could replace anything here, with your own or third party that has the same functions.

Basic

As we know the constraint before designing the Clean Architecture are :

  1. Independent of Frameworks. The architecture does not depend on the existence of some library of feature laden software. This allows you to use such frameworks as tools, rather than having to cram your system into their limited constraints.
  2. Testable. The business rules can be tested without the UI, Database, Web Server, or any other external element.
  3. Independent of UI. The UI can change easily, without changing the rest of the system. A Web UI could be replaced with a console UI, for example, without changing the business rules.
  4. Independent of Database. You can swap out Oracle or SQL Server, for Mongo, BigTable, CouchDB, or something else. Your business rules are not bound to the database.
  5. Independent of any external agency. In fact your business rules simply don’t know anything at all about the outside world.

More at https://8thlight.com/blog/uncle-bob/2012/08/13/the-clean-architecture.html

So, based on this constraint, every layer must independent and testable.

If Uncle Bob’s Architecture, has 4 layer :

  • Entities
  • Usecase
  • Controller
  • Framework & Driver

In my projects, I’m using 4 too :

  • Models
  • Repository
  • Usecase
  • Delivery

Models

Same as Entities, will used in all layer. This layer, will store any Object’s Struct and its method. Example : Article, Student, Book.
Example struct :

Any entities, or model will stored here.

Repository

Repository will store any Database handler. Querying, or Creating/ Inserting into any database will stored here. This layer will act for CRUD to database only. No business process happen here. Only plain function to Database.

This layer also have responsibility to choose what DB will used in Application. Could be Mysql, MongoDB, MariaDB, Postgresql whatever, will decided here.

If using ORM, this layer will control the input, and give it directly to ORM services.

If calling microservices, will handled here. Create HTTP Request to other services, and sanitize the data. This layer, must fully act as a repository. Handle all data input - output no specific logic happen.

This Repository layer will depends to Connected DB , or other microservices if exists.

Usecase

This layer will act as the business process handler. Any process will handled here. This layer will decide, which repository layer will use. And have responsibility to provide data to serve into delivery. Process the data doing calculation or anything will done here.

Usecase layer will accept any input from Delivery layer, that already sanitized, then process the input could be storing into DB , or Fetching from DB ,etc.

This Usecase layer will depends to Repository Layer

Delivery

This layer will act as the presenter. Decide how the data will presented. Could be as REST API, or HTML File, or gRPC whatever the delivery type.
This layer also will accept the input from user. Sanitize the input and sent it to Usecase layer.

For my sample project, I’m using REST API as the delivery method.
Client will call the resource endpoint over network, and the Delivery layer will get the input or request, and sent it to Usecase Layer.

This layer will depends to Usecase Layer.

Communications Between Layer

Except Models, each layer will communicate through inteface. For example, Usecase layer need the Repository layer, so how they communicate? Repository will provide an interface to be their contract and communication.

Example of Repository’s Interface

Usecase layer will communicate to Repository using this contract, and Repository layer MUST implement this interface so can used by Usecase

Example of Usecase’s Interface

Same with Usecase, Delivery layer will use this contract interface. And Usecase layer MUST implement this interface.

Testing Each Layer

As we know, clean means independent. Each layer testable even other layers doesn’t exist yet.

  • Models Layer
    This layer only tested if any function/method declared in any of Struct.
    And can test easily and independent to other layers.
  • Repository
    To test this layer, the better ways is doing Integrations testing. But you also can doing mocking for each test. I’m using github.com/DATA-DOG/go-sqlmock as my helper to mock query process msyql.
  • Usecase
    Because this layer depends to Repository layer, means this layer need Repository layer for testing . So we must make a mockup of Repository
    that mocked with mockery, based on the contract interface defined before.
  • Delivery
    Same with Usecase, because this layer depends to Usecase layer, means we need Usecase layer for testing. And Usecase layer also must mocked with mockery, based on the contract interface defined before

For mocking , I use mockery for golang by vektra could be seen here https://github.com/vektra/mockery

Repository Test

To test this layer, like I said before , I’m using a sql-mock to mock my query process. You can use like what I used here github.com/DATA-DOG/go-sqlmock , or another that have similar function

func TestGetByID(t *testing.T) {
db, mock, err := sqlmock.New()
if err != nil {
t.Fatalf(“an error ‘%s’ was not expected when opening a stub
database connection”, err)
}
defer db.Close()
rows := sqlmock.NewRows([]string{
“id”, “title”, “content”, “updated_at”, “created_at”}).
AddRow(1, “title 1”, “Content 1”, time.Now(), time.Now())
query := “SELECT id,title,content,updated_at, created_at FROM
article WHERE ID = \\?”
mock.ExpectQuery(query).WillReturnRows(rows) a := articleRepo.NewMysqlArticleRepository(db) num := int64(1) anArticle, err := a.GetByID(num) assert.NoError(t, err)
assert.NotNil(t, anArticle)
}

Usecase Test

Sample test for Usecase layer, that depends to Repository layer.

Mockery will generate a mockup of repository layer for me. So I don’t need to finish my Repository layer first. I can work finishing my Usecase first even my Repository layer not implemented yet.

Delivery Test

Delivery test will depends on how you to deliver the data. If using http REST API, we can use httptest a builtin package for httptest in golang.

Because it’s depends to Usecase, so we need a mock of Usecase . Same with Repository, i’m also using Mockery to mock my usecase, for delivery testing.

func TestGetByID(t *testing.T) {
var mockArticle models.Article
err := faker.FakeData(&mockArticle)
assert.NoError(t, err)
mockUCase := new(mocks.ArticleUsecase)
num := int(mockArticle.ID)
mockUCase.On(“GetByID”, int64(num)).Return(&mockArticle, nil)
e := echo.New()
req, err := http.NewRequest(echo.GET, “/article/” +
strconv.Itoa(int(num)), strings.NewReader(“”))
assert.NoError(t, err) rec := httptest.NewRecorder()
c := e.NewContext(req, rec)
c.SetPath(“article/:id”)
c.SetParamNames(“id”)
c.SetParamValues(strconv.Itoa(num))
handler:= articleHttp.ArticleHandler{
AUsecase: mockUCase,
Helper: httpHelper.HttpHelper{}
}
handler.GetByID(c)
assert.Equal(t, http.StatusOK, rec.Code)
mockUCase.AssertCalled(t, “GetByID”, int64(num))
}

Final Output and The Merging

After finish all layer and already passed on testing. You should merge into one system in main.go in root project.
Here you will define, and create every needs to environment, and merge all layers into one.

Look for my main.go as example:

You can see, every layer merge into one with its dependencies.

Conclusion :

  • In short, if drawn in a diagram, can seen below
Image for post
Image for post
  • Every library used here you can change by your own. Because the main point of clean architecture is : no matter your library, but your architecture is clean, and testable also independent
  • This is how i organized my projects, you could argue, or agree, or maybe improve this for more better, just leave a comment and share this

The Sample Projects

The sample project can seen here https://github.com/bxcodec/go-clean-arch

Libary used for my project:

  • Glide : for package management
  • go-sqlmock from github.com/DATA-DOG/go-sqlmock
  • Testify : for testing
  • Echo Labstack (Golang Web Framework) for Delivery layer
  • Viper : for environment configurations

Further Reading about Clean Architecture :

If you have a question , or need more explanation, or something, that I can not explain well here, you can ask me from my linkedin or email me. Thank you

HackerNoon.com

#BlackLivesMatter

Sign up for Get Better Tech Emails via HackerNoon.com

By HackerNoon.com

how hackers start their afternoons. the real shit is on hackernoon.com. Take a look

By signing up, you will create a Medium account if you don’t already have one. Review our Privacy Policy for more information about our privacy practices.

Check your inbox
Medium sent you an email at to complete your subscription.

Iman Tumorang

Written by

Software Engineer - Writer - Open Source Enthusiast - Startup Enthusiast. Reach me out in https://bxcodec.io for fast response :)

HackerNoon.com

Elijah McClain, George Floyd, Eric Garner, Breonna Taylor, Ahmaud Arbery, Michael Brown, Oscar Grant, Atatiana Jefferson, Tamir Rice, Bettie Jones, Botham Jean

Iman Tumorang

Written by

Software Engineer - Writer - Open Source Enthusiast - Startup Enthusiast. Reach me out in https://bxcodec.io for fast response :)

HackerNoon.com

Elijah McClain, George Floyd, Eric Garner, Breonna Taylor, Ahmaud Arbery, Michael Brown, Oscar Grant, Atatiana Jefferson, Tamir Rice, Bettie Jones, Botham Jean

Medium is an open platform where 170 million readers come to find insightful and dynamic thinking. Here, expert and undiscovered voices alike dive into the heart of any topic and bring new ideas to the surface. Learn more

Follow the writers, publications, and topics that matter to you, and you’ll see them on your homepage and in your inbox. Explore

If you have a story to tell, knowledge to share, or a perspective to offer — welcome home. It’s easy and free to post your thinking on any topic. Write on Medium

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store