How to Effectively Test GraphQL Queries and Mutations with Testify and GQLgen in Golang?

Unit Testing GraphQL in Golang

When testing GraphQL queries and mutations in a Golang application, it's crucial to have a robust testing strategy to ensure the functionality and reliability of your API endpoints.

Nestled within the labyrinth of Golang testing frameworks, testify reigns supreme as a preferred choice for its simplicity and comprehensiveness. Combined with the gqlgen/client package, which provides invaluable assistance in testing GraphQL, you can delve into the rewarding realm of effective unit testing.

Let's embark on a practical example to illuminate the process of testing GraphQL queries and mutations:

<code class="go">// graph/resolver/root.resolver_test.go

import (
    "context"
    "testing"

    "github.com/99designs/gqlgen/client"
    "github.com/99designs/gqlgen/graphql/handler"
    "github.com/mrdulin/gqlgen-cnode/graph/generated"
    "github.com/mrdulin/gqlgen-cnode/graph/model"
    "github.com/mrdulin/gqlgen-cnode/mocks"
    "github.com/stretchr/testify/mock"
    "github.com/stretchr/testify/require"
)

...

type MockedUserService struct {
    mock.Mock
}

func (s *MockedUserService) GetUserByLoginname(loginname string) *model.UserDetail {
    args := s.Called(loginname)
    return args.Get(0).(*model.UserDetail)
}

func (s *MockedUserService) ValidateAccessToken(accesstoken string) *model.UserEntity {
    args := s.Called(accesstoken)
    return args.Get(0).(*model.UserEntity)
}
...</code>

Utilizing these mock objects, we can proceed to craft comprehensive unit tests that validate the functionality of our GraphQL resolvers:

<code class="go">// graph/resolver/root.resolver_test.go

...

// TestMutationResolver_ValidateAccessToken is a test example for the ValidateAccessToken mutation.
func TestMutationResolver_ValidateAccessToken(t *testing.T) {

    t.Run("should validate accesstoken correctly", func(t *testing.T) {
        // Create a mocked user service
        mockedUserService := new(mocks.MockedUserService)

        // Inject the mocked service into our resolver
        resolvers := resolver.Resolver{UserService: mockedUserService}

        // Create a GraphQL client
        c := client.New(handler.NewDefaultServer(generated.NewExecutableSchema(generated.Config{Resolvers: &resolvers})))

        // Set up expected return values from the mock service
        ue := model.UserEntity{ID: "123", User: model.User{Loginname: &loginname, AvatarURL: &avatarURL}}
        mockedUserService.On("ValidateAccessToken", mock.AnythingOfType("string")).Return(&ue)

        // Run the GraphQL mutation query
        var resp struct {
            ValidateAccessToken struct{ ID, Loginname, AvatarUrl string }
        }
        q := `
      mutation { 
        validateAccessToken(accesstoken: "abc") { 
          id, 
          loginname, 
          avatarUrl 
        } 
      }
    `
        c.MustPost(q, &resp)

        // Assert that the mock service was called as expected
        mockedUserService.AssertExpectations(t)

        // Check the response from the GraphQL mutation
        require.Equal(t, "123", resp.ValidateAccessToken.ID)
        require.Equal(t, "mrdulin", resp.ValidateAccessToken.Loginname)
        require.Equal(t, "avatar.jpg", resp.ValidateAccessToken.AvatarUrl)
    })

}
...</code>

By implementing this testing approach, you can effectively scrutinize your GraphQL resolvers and equip your application with a solid foundation of quality and reliability.

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