Golang

Unit-tests

How You Can Make It Easy To Write Unit-Tests In Golang

When I started to write unit-tests in golang at first it wasn't easy and it was taking much time. I didn't know specific tools, technique and libraries to make easy writing of tests. Mocking interfaces was scary and caused a lot of confusion as the implemented interfaces were turned into a sprawling tree of ifs. All this led to such tests becoming difficult to maintain. Over time, I found a package testify of tools that make easy the writing of tests and also GoLand (IDE to golang) which allow you generate interface implementation. Let me show you example of that. Let's say we need to get the user data, we have the API client for that. We need to make for this client an interface and data structure and a simple function that helps us get a user.

go
type User struct {
  ID    string
  Email string
}

type SomeAPIClient interface {
  GetUser(usedId string) (*User, error)
}

func getUser(c SomeAPIClient, userID string) (*User, error) {
  return c.GetUser(userID)
}

Now this functionality can be covered with tests. First we implement our client.

go
type FakeClient struct {
  mock.Mock
}

As you can see, I have added mock.Mock to the structure so that I can mock methods when writing tests.

Now we need to implement interface GetUser we can do it via GoLand using shortkey Ctrl+I or write this

go
func (f FakeClient) GetUser(usedId string) (*User, error) {
  panic("implement me")
}

It is still raw and we need to supplement it so that our function can call this method.

go
func (f FakeClient) GetUser(usedId string) (*User, error) {
  args := f.Called(usedId)
  if args.Get(0) == nil {
    return nil, args.Error(1)
  }
  return args.Get(0).(*User), args.Error(1)
}

This implementation calls the necessary mock object, checks if it is empty, if everything is ok, then returns it.

Now let's just write our unit test.

go
func TestClient(t *testing.T) {

  assert := assert.New(t)
  testClient := new(FakeClient)

  testClient.On("GetUser", "error").Return(nil, errors.New("error"))
  u, err := getUser(testClient, "error")

  assert.Nil(u)
  assert.EqualError(err, "error")
  testClient.AssertExpectations(t)

}

What do we do here? We create a new client of API, then mock our method and in the end we check to see if everything worked out correctly.

go
Test run show us

=== RUN   TestClient
TestClient: user_test.go:32: PASS: GetUser(string)
--- PASS: TestClient (0.00s)
PASS

Add a couple more lines to our test to check we get a user

go
testUser := &User{ID: "user"}
testClient.On("GetUser", "user").Return(testUser, nil)

u, err = getUser(testClient, "user")

assert.Equal(testUser, u)
assert.Nil(err)

You can look at the example code here

17 MAY, 2020

Digital banking as a mainstream in FinTech - are you ready?

Any bank that is not ready for the digitalization should prepare to keep up with rivals. The competition is strong and demand is high. There are a lot of already transformed financial institutions into successful mobile banks and they raise their influence every day, as they operate faster and provide smarter and more efficient services.

31 NOV, 2023

How to encourage your team to participate in meetings

Our expirience with building effective and clear communication.

20 FEB, 2019

The Design Process From Idea to Product

When I started my design career, I didn’t fully understand what a design process was and how to build it. Of course, I read several articles about this topic, but this didn’t give me a complete understanding of the whole picture of the stages being built

Help Ukraine to stop russian aggression