Golang Integration Test With Gin, Gorm, Testify, PostgreSQL

Creating a comprehensive integration test setup in Golang with Gin, GORM, Testify, and PostgreSQL involves setting up a test database, writing tests for CRUD operations, and using Testify for assertions. Here’s a step-by-step guide to get you started:

Prerequisites

• Go installed
• Docker installed
• Libraries: gin-gonic/gin, gorm.io/gorm, gorm.io/driver/postgres, testify, testcontainers-go

Project Structure

myapp/
|-- main.go
|-- models/
|   |-- models.go
|-- handlers/
|   |-- handlers.go
|-- tests/
|   |-- integration_test.go
|-- go.mod
|-- go.sum

1. Setup the Models (models/models.go)

Define the models with GORM tags for database mapping.

package models

import (
    "time"
    "gorm.io/gorm"
)

type User struct {
    ID        uint           `gorm:"primaryKey"`
    Name      string         `gorm:"not null"`
    Email     string         `gorm:"unique;not null"`
    CreatedAt time.Time
}

type Book struct {
    ID            uint           `gorm:"primaryKey"`
    Title         string         `gorm:"not null"`
    Author        string         `gorm:"not null"`
    PublishedDate time.Time      `gorm:"not null"`
}

type BorrowLog struct {
    ID         uint           `gorm:"primaryKey"`
    UserID     uint           `gorm:"not null"`
    BookID     uint           `gorm:"not null"`
    BorrowedAt time.Time      `gorm:"default:CURRENT_TIMESTAMP"`
    ReturnedAt *time.Time
}

2. Setup Handlers (handlers/handlers.go)

Define the routes and handlers for CRUD operations using Gin.

package handlers

import (
    "myapp/models"
    "net/http"

    "github.com/gin-gonic/gin"
    "gorm.io/gorm"
)

type Handler struct {
    DB *gorm.DB
}

func (h *Handler) CreateUser(c *gin.Context) {
    var user models.User
    if err := c.ShouldBindJSON(&user); err != nil {
        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
        return
    }

    if err := h.DB.Create(&user).Error; err != nil {
        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
        return
    }

    c.JSON(http.StatusCreated, user)
}

func (h *Handler) GetUser(c *gin.Context) {
    var user models.User
    if err := h.DB.First(&user, c.Param("id")).Error; err != nil {
        c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
        return
    }

    c.JSON(http.StatusOK, user)
}

func (h *Handler) UpdateUser(c *gin.Context) {
    var user models.User
    if err := h.DB.First(&user, c.Param("id")).Error; err != nil {
        c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
        return
    }

    if err := c.ShouldBindJSON(&user); err != nil {
        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
        return
    }

    if err := h.DB.Save(&user).Error; err != nil {
        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
        return
    }

    c.JSON(http.StatusOK, user)
}

func (h *Handler) DeleteUser(c *gin.Context) {
    if err := h.DB.Delete(&models.User{}, c.Param("id")).Error; err != nil {
        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
        return
    }

    c.JSON(http.StatusOK, gin.H{"message": "User deleted"})
}

3. Main Application (main.go)

Set up the database connection and routes.

package main

import (
    "myapp/handlers"
    "myapp/models"
    "github.com/gin-gonic/gin"
    "gorm.io/driver/postgres"
    "gorm.io/gorm"
    "log"
    "os"
)

func main() {
    dsn := "host=localhost user=postgres password=yourpassword dbname=testdb port=5432 sslmode=disable"
    db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{})
    if err != nil {
        log.Fatalf("failed to connect to database: %v", err)
    }

    // Auto migrate the models
    db.AutoMigrate(&models.User{}, &models.Book{}, &models.BorrowLog{})

    h := handlers.Handler{DB: db}

    r := gin.Default()

    r.POST("/users", h.CreateUser)
    r.GET("/users/:id", h.GetUser)
    r.PUT("/users/:id", h.UpdateUser)
    r.DELETE("/users/:id", h.DeleteUser)

    r.Run(":8080")
}

4. Integration Test (tests/integration_test.go)

Use Testify for setting up and asserting test results.

For database we can use a Dockerized PostgreSQL instance for testing purposes, which is isolated and can be quickly torn down after tests. Here’s how to set it up in Golang using testcontainers-go:

Install testcontainers-go:

go get github.com/testcontainers/testcontainers-go

Following is the integration_test.go file that sets up a PostgreSQL container for testing:

package tests

import (
    "context"
    "fmt"
    "myapp/handlers"
    "myapp/models"
    "bytes"
    "encoding/json"
    "net/http"
    "net/http/httptest"
    "testing"
    "time"

    "github.com/gin-gonic/gin"
    "github.com/stretchr/testify/assert"
    "github.com/testcontainers/testcontainers-go"
    "github.com/testcontainers/testcontainers-go/wait"
    "gorm.io/driver/postgres"
    "gorm.io/gorm"
)

var db *gorm.DB
var h *handlers.Handler

func setupTestDB() {
    ctx := context.Background()

    // Create PostgreSQL container
    req := testcontainers.ContainerRequest{
        Image:        "postgres:latest",
        ExposedPorts: []string{"5432/tcp"},
        Env: map[string]string{
            "POSTGRES_PASSWORD": "password",
            "POSTGRES_DB":       "testdb",
        },
        WaitingFor: wait.ForListeningPort("5432/tcp").WithStartupTimeout(60 * time.Second),
    }

    postgresC, err := testcontainers.GenericContainer(ctx, testcontainers.GenericContainerRequest{
        ContainerRequest: req,
        Started:          true,
    })
    if err != nil {
        panic(err)
    }
    
    // Get the container's host and port
    host, _ := postgresC.Host(ctx)
    port, _ := postgresC.MappedPort(ctx, "5432")

    dsn := fmt.Sprintf("host=%s port=%s user=postgres password=password dbname=testdb sslmode=disable", host, port.Port())

    // Connect to the PostgreSQL database
    db, err = gorm.Open(postgres.Open(dsn), &gorm.Config{})
    if err != nil {
        panic("failed to connect to database")
    }

    // Migrate the schema
    db.AutoMigrate(&models.User{}, &models.Book{}, &models.BorrowLog{})

    // Initialize the handler
    h = &handlers.Handler{DB: db}

    // Clean up database before each test
    db.Exec("DELETE FROM users")

    // Tear down the container after tests
    defer postgresC.Terminate(ctx)
}

func TestCreateUser(t *testing.T) {
    setupTestDB()

    r := gin.Default()
    r.POST("/users", h.CreateUser)

    user := models.User{
        Name:  "Test User",
        Email: "testuser@example.com",
    }

    jsonData, _ := json.Marshal(user)
    req, _ := http.NewRequest(http.MethodPost, "/users", bytes.NewBuffer(jsonData))
    req.Header.Set("Content-Type", "application/json")

    w := httptest.NewRecorder()
    r.ServeHTTP(w, req)

    assert.Equal(t, http.StatusCreated, w.Code)

    var createdUser models.User
    err := json.Unmarshal(w.Body.Bytes(), &createdUser)
    assert.Nil(t, err)
    assert.Equal(t, user.Name, createdUser.Name)
    assert.Equal(t, user.Email, createdUser.Email)
}

func TestGetUser(t *testing.T) {
    setupTestDB()

    // Create a user
    user := models.User{
        Name:  "Test User",
        Email: "testuser@example.com",
    }
    db.Create(&user)

    r := gin.Default()
    r.GET("/users/:id", h.GetUser)

    req, _ := http.NewRequest(http.MethodGet, fmt.Sprintf("/users/%d", user.ID), nil)
    w := httptest.NewRecorder()
    r.ServeHTTP(w, req)

    assert.Equal(t, http.StatusOK, w.Code)

    var fetchedUser models.User
    err := json.Unmarshal(w.Body.Bytes(), &fetchedUser)
    assert.Nil(t, err)
    assert.Equal(t, user.Name, fetchedUser.Name)
    assert.Equal(t, user.Email, fetchedUser.Email)
}

func TestUpdateUser(t *testing.T) {
    setupTestDB()

    // Create a user to be updated.
    user := models.User{
        Name:  "Original User",
        Email: "original@example.com",
    }
    db.Create(&user)

    r := gin.Default()
    r.PUT("/users/:id", h.UpdateUser)

    updatedData := models.User{
        Name:  "Updated User",
        Email: "updated@example.com",
    }

    jsonData, _ := json.Marshal(updatedData)
    req, _ := http.NewRequest(http.MethodPut, fmt.Sprintf("/users/%d", user.ID), bytes.NewBuffer(jsonData))
    req.Header.Set("Content-Type", "application/json")

    w := httptest.NewRecorder()
    r.ServeHTTP(w, req)

    assert.Equal(t, http.StatusOK, w.Code)

    var updatedUser models.User
    err := json.Unmarshal(w.Body.Bytes(), &updatedUser)
    assert.Nil(t, err)
    assert.Equal(t, updatedData.Name, updatedUser.Name)
    assert.Equal(t, updatedData.Email, updatedUser.Email)

    // Verify that the user is actually updated in the database.
    var userInDB models.User
    db.First(&userInDB, user.ID)
    assert.Equal(t, updatedData.Name, userInDB.Name)
    assert.Equal(t, updatedData.Email, userInDB.Email)
}

func TestDeleteUser(t *testing.T) {
    setupTestDB()

    // Create a user to be deleted.
    user := models.User{
        Name:  "Delete User",
        Email: "delete@example.com",
    }
    db.Create(&user)

    r := gin.Default()
    r.DELETE("/users/:id", h.DeleteUser)

    req, _ := http.NewRequest(http.MethodDelete, fmt.Sprintf("/users/%d", user.ID), nil)
    w := httptest.NewRecorder()
    r.ServeHTTP(w, req)

    assert.Equal(t, http.StatusOK, w.Code)

    // Verify the response message.
    var response map[string]string
    err := json.Unmarshal(w.Body.Bytes(), &response)
    assert.Nil(t, err)
    assert.Equal(t, "User deleted", response["message"])

    // Verify that the user is actually deleted from the database.
    var userInDB models.User
    result := db.First(&userInDB, user.ID)
    assert.Error(t, result.Error)
    assert.Equal(t, gorm.ErrRecordNotFound, result.Error)
}

Explanation

• SetupTestDB: Sets up a PostgreSQL database connection using GORM for testing.
• TestCreateUser: Sends a POST request to create a new user and asserts the response.
• TestGetUser: Retrieves a user by ID and checks that the data matches what was inserted.
• TestUpdateUser:
  • Creates a user and updates it using the PUT /users/:id endpoint.
  • Asserts that the response status is 200 OK.
  • Verifies that the user's details are updated in the response.
  • Fetches the user from the database and confirms that the changes are persisted.
• TestDeleteUser:
  • Creates a user and deletes it using the DELETE /users/:id endpoint.
  • Asserts that the response status is 200 OK and checks for a success message.
  • Attempts to fetch the deleted user from the database to ensure the user no longer exists, asserting an error of gorm.ErrRecordNotFound.
• testcontainers-go: This library allows you to spin up Docker containers directly from your Go code. It's ideal for creating a temporary PostgreSQL instance for integration tests.
• setupTestDB: This function starts a PostgreSQL Docker container, connects to it using gorm, and sets up the database schema. It also ensures that the container is cleaned up after the tests are finished.
• defer postgresC.Terminate(ctx): Ensures that the PostgreSQL container is terminated after tests are done, simulating an in-memory approach.
• Dynamic Host and Port: Uses the container's dynamically allocated host and port for connecting to the database.

Running the Tests

Run the tests using:

go test ./tests -v

Benefits of Using testcontainers-go:

1. Isolation: Each test run gets a fresh PostgreSQL instance, ensuring no data leakage between tests.
2. Replicates Production Environment: Testing against a real PostgreSQL instance provides more reliable results than using an in-memory database.
3. Automation: Automatically starts and stops the PostgreSQL container, making it easy to use in CI/CD pipelines.

Key Points

• Using a Test Database: It's a good practice to use a separate PostgreSQL database (ex: containerized ones) for testing to avoid affecting production data.
• Setup and Cleanup: Ensure to clean up the database between tests to maintain consistency.
• Testify: Provides powerful assertion methods for validating the results.
• Gin's Test Server: Uses httptest for simulating HTTP requests against the Gin server.

With this setup, you can test CRUD operations for a User model, ensuring the API works as expected with PostgreSQL. You can expand the tests similarly for Book and BorrowLog models.

If you found this helpful, let me know by leaving a 👍 or a comment!, or if you think this post could help someone, feel free to share it! Thank you very much! 😃