dockertest.go

func SetupDatabase(t *testing.T) (func(), *sql.DB) {
	pool, _ := dockertest.NewPool("")

	# specify the container image here
	postgres, _ := pool.RunWithOptions(&dockertest.RunOptions{
		Repository: "postgres",
		Tag:        "13.2",
		Env: []string{
			"POSTGRES_USER=postgres",
			"POSTGRES_PASSWORD=password",
		},
	}, func(config *docker.HostConfig) {
		config.AutoRemove = true
		config.RestartPolicy = docker.RestartPolicy{
			Name: "no",
		}
	})

	opts := flag.NewDefaultPostgresOpts()

	# get the container port
	opts.PostgresPort, _ = strconv.Atoi(postgres.GetPort("5432/tcp"))

	var conn *sql.DB
	if err := pool.Retry(func() error {
		conn, err = sql.Open("postgres", opts.ConnectionString())
		if err != nil {
			return err
		}
		return conn.Ping()
	}); err != nil {
		t.Errorf("Could not connect to database: %s", err)
		t.FailNow()
	}

	# this func() is the teardown function after the test
	return func() {
		if err := pool.Purge(postgres); err != nil {
			log.Fatalf("Could not purge resource: %s", err)
		}
	}, conn
}

# now we can use this function to launch a real database in the test
func TestSomething(t *testing.T) {
	teardown, conn := unittest.SetupDatabase(t)
	defer teardown()

	# use conn
	conn.Exec(...)
}