chore(tests): faster and more stable tests by moving db setup to TestMain (#11)

By using [TestMain](https://pkg.go.dev/testing#hdr-Main) to create the
test database and cleanup on test exit, reduce test execution time and
improve stability.

Previously, spinning up new docker container for each test incurred lots
of time costs, and tests would fail 6 out of 10 times.

![image](https://github.com/oolio-group/dynago/assets/4880359/cdf25ce7-330a-433c-9178-2780502ec20b)

Author: shidil

tests/client_test.go

@@ -3,21 +3,22 @@ package tests
 import (
 	"context"
 	"fmt"
-	"github.com/oolio-group/dynago"
 	"log"
+	"os"
 	"testing"
 
+	"github.com/oolio-group/dynago"
+	"github.com/ory/dockertest/v3"
+
 	"github.com/aws/aws-sdk-go-v2/aws"
 	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
 	"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
-	"github.com/ory/dockertest/v3"
 )
 
-func startLocalDatabase(t *testing.T) (addr string, purge func()) {
-	t.Helper()
+func startLocalDatabase() (addr string, purge func()) {
 	pool, err := dockertest.NewPool("")
 	if err != nil {
-		t.Fatalf("could not connect to docker: %s", err)
+		log.Fatalln("could not connect to docker", err)
 	}
 
 	resource, err := pool.Run("amazon/dynamodb-local", "latest", []string{})
@@ -27,11 +28,23 @@ func startLocalDatabase(t *testing.T) (addr string, purge func()) {
 	addr = fmt.Sprintf("http://localhost:%s", resource.GetPort("8000/tcp"))
 	return addr, func() {
 		if err := pool.Purge(resource); err != nil {
-			t.Fatalf("could not purge container: %s", err)
+			log.Println(err)
 		}
 	}
 }
 
+var dynamoEndpoint string
+
+func TestMain(m *testing.M) {
+	address, cleanup := startLocalDatabase()
+	dynamoEndpoint = address
+
+	code := m.Run()
+	// os.Exit does not respect defer
+	cleanup()
+	os.Exit(code)
+}
+
 func createTestTable(t *dynago.Client) error {
 	_, err := t.GetDynamoDBClient().CreateTable(context.TODO(), &dynamodb.CreateTableInput{
 		AttributeDefinitions: []types.AttributeDefinition{{
@@ -73,13 +86,10 @@ func TestNewClient(t *testing.T) {
 }
 
 func TestNewClientLocalEndpoint(t *testing.T) {
-	endpoint, purge := startLocalDatabase(t)
-	defer purge()
-
 	table, err := dynago.NewClient(context.TODO(), dynago.ClientOptions{
 		TableName: "test",
 		Endpoint: &dynago.EndpointResolver{
-			EndpointURL:     endpoint,
+			EndpointURL:     dynamoEndpoint,
 			AccessKeyID:     "dummy",
 			SecretAccessKey: "dummy",
 		},

tests/query_test.go

@@ -46,10 +46,7 @@ type User struct {
 }
 
 func TestQuery(t *testing.T) {
-	endoint, purge := startLocalDatabase(t)
-	defer purge()
-
-	table := prepareTable(t, endoint, "query_test")
+	table := prepareTable(t, dynamoEndpoint, "query_test")
 	testCases := []struct {
 		title       string
 		condition   string
@@ -245,10 +242,7 @@ func genRandomBytes(t *testing.T, size int) (blk []byte) {
 }
 
 func TestQueryPagination(t *testing.T) {
-	endoint, purge := startLocalDatabase(t)
-	defer purge()
-
-	table := prepareTable(t, endoint, "query_pagination_test")
+	table := prepareTable(t, dynamoEndpoint, "query_pagination_test")
 	// write 3MB worth of sample user records to the database for testing
 	// dynamodb paginates query result by pages of 1MB recors by default.
 	const batchSize = 100

tests/transact_items_test.go

@@ -17,10 +17,7 @@ type Terminal struct {
 }
 
 func TestTransactItems(t *testing.T) {
-	endoint, purge := startLocalDatabase(t)
-	defer purge()
-
-	table := prepareTable(t, endoint, "transcact_item_test")
+	table := prepareTable(t, dynamoEndpoint, "transcact_item_test")
 
 	testCases := []struct {
 		title     string