How do you write integration tests for a Go service that depends on a PostgreSQL database?

Question

Accepted Answer

//go:build integration

package repository_test

import (
    "context"
    "testing"
    "github.com/testcontainers/testcontainers-go/modules/postgres"
)

var testDB *sql.DB

func TestMain(m *testing.M) {
    ctx := context.Background()

// Start Postgres container
    container, err := postgres.RunContainer(ctx,
        testcontainers.WithImage("postgres:16-alpine"),
        postgres.WithDatabase("testdb"),
        postgres.WithUsername("test"),
        postgres.WithPassword("test"),
        testcontainers.WithWaitStrategy(
            wait.ForLog("database system is ready to accept connections"),
        ),
    )
    if err != nil { log.Fatal(err) }
    defer container.Terminate(ctx)

connStr, _ := container.ConnectionString(ctx, "sslmode=disable")
    testDB, _ = sql.Open("pgx", connStr)

// Run migrations
    runMigrations(testDB)

os.Exit(m.Run())
}

func TestUserRepo_Create(t *testing.T) {
    // Each test gets an isolated transaction
    tx, _ := testDB.Begin()
    defer tx.Rollback() // always rolled back — no test pollution

repo := NewPostgresUserRepo(tx)
    user := &User{Name: "Alice", Email: "alice@test.com"}

err := repo.Create(context.Background(), user)
    if err != nil { t.Fatalf("Create: %v", err) }

got, err := repo.FindByEmail(context.Background(), "alice@test.com")
    if err != nil { t.Fatalf("FindByEmail: %v", err) }
    if got.Name != "Alice" { t.Errorf("want Alice, got %s", got.Name) }
} Build tag //go:build integration keeps integration tests separate from unit tests Transaction rollback per test ensures test isolation without truncating tables TestMain sets up the container once per test suite — not per test case Pass tx (implementing DBTX interface) to the repository — works transparently Run in CI with: go test -tags=integration ./...

How do you write integration tests for a Go service that depends on a PostgreSQL database?

Use testcontainers-go to spin up a real Postgres container per test suite, run migrations, and wrap each test in a transaction that is rolled back at the end for isolation.

How do you write integration tests for a Go service that depends on a PostgreSQL database?

Use testcontainers-go to spin up a real Postgres container per test suite, run migrations, and wrap each test in a transaction that is rolled back at the end for isolation.

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