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Getting started with Testcontainers for Go

Learn how to create a Go application and test database interactions using Testcontainers for Go with a real PostgreSQL instance.

Go Testing with Docker

20 minutes

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Create the project

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Write tests

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Reuse containers with test suites

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---

In the previous section, you saw how to spin up a Postgres Docker container for a single test. But often you have multiple tests in a single file, and you may want to reuse the same Postgres Docker container for all of them.

You can use the testify suite package to implement common test setup and teardown actions.

Extract container setup

First, extract the PostgresContainer creation logic into a separate file called testhelpers/containers.go:

package testhelpers

import (
	"context"
	"path/filepath"
	"testing"

	"github.com/stretchr/testify/require"
	"github.com/testcontainers/testcontainers-go"
	"github.com/testcontainers/testcontainers-go/modules/postgres"
)

type PostgresContainer struct {
	*postgres.PostgresContainer
	ConnectionString string
}

func CreatePostgresContainer(t *testing.T, ctx context.Context) *PostgresContainer {
	t.Helper()

	ctr, err := postgres.Run(ctx,
		"postgres:16-alpine",
		postgres.WithInitScripts(filepath.Join("..", "testdata", "init-db.sql")),
		postgres.WithDatabase("test-db"),
		postgres.WithUsername("postgres"),
		postgres.WithPassword("postgres"),
		postgres.BasicWaitStrategies(),
	)
	testcontainers.CleanupContainer(t, ctr)
	require.NoError(t, err)

	connStr, err := ctr.ConnectionString(ctx, "sslmode=disable")
	require.NoError(t, err)

	return &PostgresContainer{
		PostgresContainer: ctr,
		ConnectionString:  connStr,
	}
}

In containers.go, PostgresContainer extends the testcontainers-go PostgresContainer to provide easy access to ConnectionString. The CreatePostgresContainer() function accepts *testing.T as its first parameter, calls t.Helper() so that test failures point to the caller, and uses testcontainers.CleanupContainer() to register automatic cleanup.

Write the test suite

Create customer/repo_suite_test.go and implement tests for creating a customer and getting a customer by email using the testify suite package:

package customer

import (
	"context"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"github.com/stretchr/testify/suite"
	"github.com/testcontainers/testcontainers-go-demo/testhelpers"
)

type CustomerRepoTestSuite struct {
	suite.Suite
	pgContainer *testhelpers.PostgresContainer
	repository  *Repository
	ctx         context.Context
}

func (suite *CustomerRepoTestSuite) SetupSuite() {
	suite.ctx = context.Background()
	suite.pgContainer = testhelpers.CreatePostgresContainer(suite.T(), suite.ctx)

	repository, err := NewRepository(suite.ctx, suite.pgContainer.ConnectionString)
	require.NoError(suite.T(), err)
	suite.repository = repository
}

func (suite *CustomerRepoTestSuite) TestCreateCustomer() {
	t := suite.T()

	customer, err := suite.repository.CreateCustomer(suite.ctx, Customer{
		Name:  "Henry",
		Email: "henry@gmail.com",
	})
	require.NoError(t, err)
	assert.NotNil(t, customer.Id)
}

func (suite *CustomerRepoTestSuite) TestGetCustomerByEmail() {
	t := suite.T()

	customer, err := suite.repository.GetCustomerByEmail(suite.ctx, "john@gmail.com")
	require.NoError(t, err)
	assert.Equal(t, "John", customer.Name)
	assert.Equal(t, "john@gmail.com", customer.Email)
}

func TestCustomerRepoTestSuite(t *testing.T) {
	suite.Run(t, new(CustomerRepoTestSuite))
}

Here's what the code does:

• CustomerRepoTestSuite extends suite.Suite and includes fields shared across multiple tests.
• SetupSuite() runs once before all tests. It calls CreatePostgresContainer(suite.T(), ...) which handles cleanup registration automatically via CleanupContainer, so no TearDownSuite() is needed.
• TestCreateCustomer() uses require.NoError() for the create operation (fail immediately if it errors) and assert.NotNil() for the ID check.
• TestGetCustomerByEmail() uses require.NoError() then asserts on the returned values.
• TestCustomerRepoTestSuite(t *testing.T) runs the test suite when you execute go test.

Tip

For the purpose of this guide, the tests don't reset data in the database. In practice, it's a good idea to reset the database to a known state before running each test.

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