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:

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

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:

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

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.

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