testcontainers

When I was working on a Zipkin PR I discovered a nice Java library called testcontainers.

It provides an easy and clean API over the go docker sdk to run, terminate and connect to containers in your tests.

I found myself comfortable programmatically writing the containers I need to run an integration/smoke tests. So I started porting this library in Go.

This is the API I have defined:

package main

import (
	"context"
	"fmt"
	"net/http"
	"testing"

	"github.com/testcontainers/testcontainers-go"
	"github.com/testcontainers/testcontainers-go/wait"
)

func TestNginxLatestReturn(t *testing.T) {
	ctx := context.Background()
	req := testcontainers.ContainerRequest{
		Image:        "nginx",
		ExposedPorts: []string{"80/tcp"},
		WaitingFor:   wait.ForHTTP("/"),
	}
	nginxC, err := testcontainers.GenericContainer(ctx, testcontainers.GenericContainerRequest{
		ContainerRequest: req,
		Started:          true,
	})
	if err != nil {
		t.Error(err)
	}
	defer nginxC.Terminate(ctx)
	ip, err := nginxC.Host(ctx)
	if err != nil {
		t.Error(err)
	}
	port, err := nginxC.MappedPort(ctx, "80")
	if err != nil {
		t.Error(err)
	}
	resp, err := http.Get(fmt.Sprintf("http://%s:%s", ip, port.Port()))
	if resp.StatusCode != http.StatusOK {
		t.Errorf("Expected status code %d. Got %d.", http.StatusOK, resp.StatusCode)
	}
}

This is a simple example, you can create one container in my case using the nginx image. You can get its IP ip, err := nginxC.GetContainerIpAddress(ctx) and you can use it to make a GET: resp, err := http.Get(fmt.Sprintf("http://%s", ip))

To clean your environment you can defer the container termination defer nginxC.Terminate(ctx, t). t is *testing.T and it is used to notify is the defer failed marking the test as failed.

You can build more complex flow using env var to configure the containers. Let's suppose you are testing an application that requires redis:

func TestRedisPing(t *testing.T) {
	ctx := context.Background()
	req := testcontainers.ContainerRequest{
		Image:        "redis",
		ExposedPorts: []string{"6379/tcp"},
	}
	redisC, err := testcontainers.GenericContainer(ctx, testcontainers.GenericContainerRequest{
		ContainerRequest: req,
		Started:          true,
	})
	if err != nil {
		t.Error(err)
	}
	defer redisC.Terminate(ctx)
	ip, err := redisC.Host(ctx)
	if err != nil {
		t.Error(err)
	}
	redisPort, err := redisC.MappedPort(ctx, "6479/tcp")
	if err != nil {
		t.Error(err)
	}

	appReq := testcontainers.ContainerRequest{
		ExposedPorts: []string{"8081/tcp"},
		Env: map[string]string{
			"REDIS_HOST": fmt.Sprintf("http://%s:%s", ip, redisPort.Port()),
		},
	}
	appC, err := testcontainers.RunContainer(ctx, "your/app", testcontainers.GenericContainerRequest{
		ContainerRequest: appReq,
		Started:          true,
	})
	if err != nil {
		t.Error(err)
	}
	defer appC.Terminate(ctx)

	// your assertions
}