Publish an example testing go code with Postgres

testingpg/testingpg.go

@@ -0,0 +1,116 @@
+// Copyright (c) 2023 Vasiliy Vasilyuk. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package testingpg
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"os"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/stretchr/testify/require"
+)
+
+type TestingT interface {
+	require.TestingT
+
+	Logf(format string, args ...any)
+	Cleanup(f func())
+}
+
+func New(t TestingT) *Postgres {
+	return newPostgres(t).cloneFromReference(t)
+}
+
+type Postgres struct {
+	url string
+	ref string
+
+	conn *pgxpool.Pool
+}
+
+func newPostgres(t TestingT) *Postgres {
+	urlStr := os.Getenv("TESTING_DB_URL")
+	if urlStr == "" {
+		urlStr = "postgresql://postgres:postgres@localhost:32260/postgres?sslmode=disable"
+		const format = "env TESTING_DB_URL is empty, used default value: %s"
+		t.Logf(format, urlStr)
+	}
+
+	refDatabase := os.Getenv("TESTING_DB_REF")
+	if refDatabase == "" {
+		refDatabase = "reference"
+	}
+
+	pool, err := pgxpool.New(context.Background(), urlStr)
+	require.NoError(t, err)
+
+	return &Postgres{
+		url: urlStr,
+		ref: refDatabase,
+
+		conn: pool,
+	}
+}
+
+func (p *Postgres) URL() string {
+	return p.url
+}
+
+func (p *Postgres) PgxPool() *pgxpool.Pool {
+	return p.conn
+}
+
+func (p *Postgres) cloneFromReference(t TestingT) *Postgres {
+	cfg, err := pgxpool.ParseConfig(p.url)
+	require.NoError(t, err)
+
+	pool, err := pgxpool.New(context.Background(), p.url)
+	require.NoError(t, err)
+
+	newDatabaseName := uuid.New().String()
+
+	const sqlTemplate = `CREATE DATABASE %q WITH TEMPLATE %s OWNER %s;`
+	sql := fmt.Sprintf(
+		sqlTemplate,
+		newDatabaseName,
+		p.ref,
+		cfg.ConnConfig.User,
+	)
+	_, err = pool.Exec(context.Background(), sql)
+	require.NoError(t, err)
+
+	// Automatically drop database copy after the test is completed.
+	t.Cleanup(func() {
+		sql := fmt.Sprintf(`DROP DATABASE %q WITH (FORCE);`, newDatabaseName)
+
+		ctx, done := context.WithTimeout(context.Background(), time.Minute)
+		defer done()
+
+		_, err := p.conn.Exec(ctx, sql)
+		require.NoError(t, err)
+	})
+
+	urlString := replaceDBName(t, cfg, newDatabaseName)
+	newPool, err := pgxpool.New(context.Background(), urlString)
+	require.NoError(t, err)
+
+	return &Postgres{
+		url: urlString,
+		ref: newDatabaseName,
+
+		conn: newPool,
+	}
+}
+
+func replaceDBName(t TestingT, cfg *pgxpool.Config, dbname string) string {
+	r, err := url.Parse(cfg.ConnString())
+	require.NoError(t, err)
+	r.Path = dbname
+	return r.String()
+}

testingpg/testingpg_test.go

@@ -0,0 +1,95 @@
+// Copyright (c) 2023 Vasiliy Vasilyuk. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package testingpg_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/stretchr/testify/require"
+
+	"github.com/xorcare/testing-go-code-with-postgres/testingpg"
+)
+
+func TestNewPostgres(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping test in short mode")
+	}
+
+	t.Parallel()
+
+	t.Run("Successfully connect by URL and get version", func(t *testing.T) {
+		t.Parallel()
+
+		// Arrange
+		postgres := testingpg.New(t)
+
+		ctx := context.Background()
+		dbPool, err := pgxpool.New(ctx, postgres.URL())
+		require.NoError(t, err)
+
+		// Act
+		var version string
+		err = dbPool.QueryRow(ctx, "SELECT version();").Scan(&version)
+
+		// Assert
+		require.NoError(t, err)
+		require.NotEmpty(t, version)
+		t.Log(version)
+	})
+
+	t.Run("Successfully obtained a version using a pre-configured conn", func(t *testing.T) {
+		t.Parallel()
+
+		// Arrange
+		postgres := testingpg.New(t)
+		ctx := context.Background()
+
+		// Act
+		var version string
+		err := postgres.PgxPool().QueryRow(ctx, "SELECT version();").Scan(&version)
+
+		// Assert
+		require.NoError(t, err)
+		require.NotEmpty(t, version)
+
+		t.Log(version)
+	})
+
+	t.Run("Changes are not visible in different instances", func(t *testing.T) {
+		t.Parallel()
+
+		// Arrange
+		postgres1 := testingpg.New(t)
+		postgres2 := testingpg.New(t)
+
+		ctx := context.Background()
+
+		// Act
+		const sql = `CREATE TABLE "no_conflict" (id integer PRIMARY KEY)`
+		_, err1 := postgres1.PgxPool().Exec(ctx, sql)
+		_, err2 := postgres2.PgxPool().Exec(ctx, sql)
+
+		// Assert
+		require.NoError(t, err1)
+		require.NoError(t, err2, "databases must be isolated for each instance")
+	})
+
+	t.Run("URL is different at different instances", func(t *testing.T) {
+		t.Parallel()
+
+		// Arrange
+		postgres1 := testingpg.New(t)
+		postgres2 := testingpg.New(t)
+
+		// Act
+		url1 := postgres1.URL()
+		url2 := postgres2.URL()
+
+		// Assert
+		require.NotEqual(t, url1, url2)
+	})
+}