test: remove private api usages in tests

refactor tests, so private interfaces are not used:
* split batches in tests
* remove batchSplitter interface, which is not used after refactor
* replace quoteKeyword with simple substitution. it is not needed as
  table names in tests are not problematic

I need this for a lib/tests module split

clickhouse.go

@@ -84,12 +84,6 @@ func (h *clickhouse) disableReferentialIntegrity(db *sql.DB, loadFn loadFunction
 	return tx.Commit()
 }
 
-// splitter is a batchSplitter interface implementation. We need it for
-// ClickHouseDB because clickhouse doesn't support multi-statements.
-func (*clickhouse) splitter() []byte {
-	return []byte(";\n")
-}
-
 func (h *clickhouse) cleanTableQuery(tableName string) string {
 	if h.cleanTableFn == nil {
 		return h.baseHelper.cleanTableQuery(tableName)

clickhouse_test.go

@@ -1,5 +1,4 @@
 //go:build clickhouse
-// +build clickhouse
 
 package testfixtures
 
@@ -11,10 +10,7 @@ import (
 )
 
 func TestClickhouse(t *testing.T) {
-	testLoader(
-		t,
-		"clickhouse",
-		os.Getenv("CLICKHOUSE_CONN_STRING"),
-		"testdata/schema/clickhouse.sql",
-	)
+	db := openDB(t, "clickhouse", os.Getenv("CLICKHOUSE_CONN_STRING"))
+	loadSchemaInBatchesBySplitter(t, db, "testdata/schema/clickhouse.sql", []byte(";\n"))
+	testLoader(t, db, "clickhouse")
 }

cockroachdb_test.go

@@ -1,5 +1,4 @@
 //go:build cockroachdb
-// +build cockroachdb
 
 package testfixtures
 
@@ -13,11 +12,12 @@ import (
 
 func TestCockroachDB(t *testing.T) {
 	for _, dialect := range []string{"postgres", "pgx"} {
+		db := openDB(t, dialect, os.Getenv("CRDB_CONN_STRING"))
+		loadSchemaInOneQuery(t, db, "testdata/schema/cockroachdb.sql")
 		testLoader(
 			t,
+			db,
 			dialect,
-			os.Getenv("CRDB_CONN_STRING"),
-			"testdata/schema/cockroachdb.sql",
 			DangerousSkipTestDatabaseCheck(),
 			UseDropConstraint(),
 		)

helper.go

@@ -34,16 +34,6 @@ type queryable interface {
 	QueryRow(string, ...interface{}) *sql.Row
 }
 
-// batchSplitter is an interface with method which returns byte slice for
-// splitting SQL batches. This need to split sql statements and run its
-// separately.
-//
-// For Microsoft SQL Server batch splitter is "GO". For details see
-// https://docs.microsoft.com/en-us/sql/t-sql/language-elements/sql-server-utilities-statements-go
-type batchSplitter interface { //nolint
-	splitter() []byte
-}
-
 var (
 	_ helper = &clickhouse{}
 	_ helper = &spanner{}

mysql_test.go

@@ -1,4 +1,4 @@
-// +build mysql
+//go:build mysql
 
 package testfixtures
 
@@ -10,10 +10,7 @@ import (
 )
 
 func TestMySQL(t *testing.T) {
-	testLoader(
-		t,
-		"mysql",
-		os.Getenv("MYSQL_CONN_STRING"),
-		"testdata/schema/mysql.sql",
-	)
+	db := openDB(t, "mysql", os.Getenv("MYSQL_CONN_STRING"))
+	loadSchemaInOneQuery(t, db, "testdata/schema/mysql.sql")
+	testLoader(t, db, "mysql")
 }

postgresql_test.go

@@ -1,4 +1,4 @@
-// +build postgresql
+//go:build postgresql
 
 package testfixtures
 
@@ -11,36 +11,28 @@ import (
 )
 
 func TestPostgreSQL(t *testing.T) {
-	for _, dialect := range []string{"postgres", "pgx"} {
-		testLoader(
-			t,
-			dialect,
-			os.Getenv("PG_CONN_STRING"),
-			"testdata/schema/postgresql.sql",
-		)
-	}
+	testPostgreSQL(t)
 }
 
 func TestPostgreSQLWithAlterConstraint(t *testing.T) {
-	for _, dialect := range []string{"postgres", "pgx"} {
-		testLoader(
-			t,
-			dialect,
-			os.Getenv("PG_CONN_STRING"),
-			"testdata/schema/postgresql.sql",
-			UseAlterConstraint(),
-		)
-	}
+	testPostgreSQL(t, UseAlterConstraint())
 }
 
 func TestPostgreSQLWithDropConstraint(t *testing.T) {
+	testPostgreSQL(t, UseDropConstraint())
+}
+
+func testPostgreSQL(t *testing.T, additionalOptions ...func(*Loader) error) {
+	t.Helper()
 	for _, dialect := range []string{"postgres", "pgx"} {
+		db := openDB(t, dialect, os.Getenv("PG_CONN_STRING"))
+		loadSchemaInOneQuery(t, db, "testdata/schema/postgresql.sql")
 		testLoader(
 			t,
+			db,
 			dialect,
-			os.Getenv("PG_CONN_STRING"),
-			"testdata/schema/postgresql.sql",
-			UseDropConstraint(),
+			additionalOptions...,
 		)
 	}
+
 }

spanner.go

@@ -84,12 +84,6 @@ func (h *spanner) disableReferentialIntegrity(db *sql.DB, loadFn loadFunction) (
 	return h.dropAndRecreateConstraints(db, loadFn)
 }
 
-// splitter is a batchSplitter interface implementation. We need it for
-// spanner because spanner doesn't support multi-statements.
-func (*spanner) splitter() []byte {
-	return []byte(";\n")
-}
-
 func (h *spanner) cleanTableQuery(tableName string) string {
 	if h.cleanTableFn == nil {
 		return h.baseHelper.cleanTableQuery(tableName)

spanner_test.go

@@ -18,13 +18,9 @@ import (
 func TestSpanner(t *testing.T) {
 	prepareSpannerDB(t)
 
-	testLoader(
-		t,
-		"spanner",
-		os.Getenv("SPANNER_CONN_STRING"),
-		"testdata/schema/spanner.sql",
-		DangerousSkipTestDatabaseCheck(),
-	)
+	db := openDB(t, "spanner", os.Getenv("SPANNER_CONN_STRING"))
+	loadSchemaInBatchesBySplitter(t, db, "testdata/schema/spanner.sql", []byte(";\n"))
+	testLoader(t, db, "spanner", DangerousSkipTestDatabaseCheck())
 }
 
 func prepareSpannerDB(t *testing.T) {

sqlite_test.go

@@ -1,4 +1,4 @@
-// +build sqlite
+//go:build sqlite
 
 package testfixtures
 
@@ -10,10 +10,7 @@ import (
 )
 
 func TestSQLite(t *testing.T) {
-	testLoader(
-		t,
-		"sqlite3",
-		os.Getenv("SQLITE_CONN_STRING"),
-		"testdata/schema/sqlite.sql",
-	)
+	db := openDB(t, "sqlite3", os.Getenv("SQLITE_CONN_STRING"))
+	loadSchemaInOneQuery(t, db, "testdata/schema/sqlite.sql")
+	testLoader(t, db, "sqlite3")
 }

sqlserver.go

@@ -143,11 +143,3 @@ func (h *sqlserver) disableReferentialIntegrity(db *sql.DB, loadFn loadFunction)
 
 	return tx.Commit()
 }
-
-// splitter is a batchSplitter interface implementation. We need it for
-// SQL Server because commands like a `CREATE SCHEMA...` and a `CREATE TABLE...`
-// could not be executed in the same batch.
-// See https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms175502(v=sql.105)#rules-for-using-batches
-func (*sqlserver) splitter() []byte {
-	return []byte("GO\n")
-}

sqlserver_test.go

@@ -1,4 +1,4 @@
-// +build sqlserver
+//go:build sqlserver
 
 package testfixtures
 
@@ -10,21 +10,21 @@ import (
 )
 
 func TestSQLServer(t *testing.T) {
-	testLoader(
-		t,
-		"sqlserver",
-		os.Getenv("SQLSERVER_CONN_STRING"),
-		"testdata/schema/sqlserver.sql",
-		DangerousSkipTestDatabaseCheck(),
-	)
+	testSQLServer(t, "sqlserver")
 }
 
 func TestDeprecatedMssql(t *testing.T) {
+	testSQLServer(t, "mssql")
+}
+
+func testSQLServer(t *testing.T, dialect string) {
+	t.Helper()
+	db := openDB(t, dialect, os.Getenv("SQLSERVER_CONN_STRING"))
+	loadSchemaInBatchesBySplitter(t, db, "testdata/schema/sqlserver.sql", []byte("GO\n"))
 	testLoader(
 		t,
-		"mssql",
-		os.Getenv("SQLSERVER_CONN_STRING"),
-		"testdata/schema/sqlserver.sql",
+		db,
+		dialect,
 		DangerousSkipTestDatabaseCheck(),
 	)
 }

testfixtures_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"database/sql"
 	"embed"
+	"errors"
 	"fmt"
 	"os"
 	"testing"
@@ -26,64 +27,70 @@ func TestFixtureFile(t *testing.T) {
 func TestRequiredOptions(t *testing.T) {
 	t.Run("DatabaseIsRequired", func(t *testing.T) {
 		_, err := New()
-		if err != errDatabaseIsRequired {
+		if !errors.Is(err, errDatabaseIsRequired) {
 			t.Error("should return an error if database if not given")
 		}
 	})
 
 	t.Run("DialectIsRequired", func(t *testing.T) {
 		_, err := New(Database(&sql.DB{}))
-		if err != errDialectIsRequired {
+		if !errors.Is(err, errDialectIsRequired) {
 			t.Error("should return an error if dialect if not given")
 		}
 	})
 }
 
-func testLoader(t *testing.T, dialect, connStr, schemaFilePath string, additionalOptions ...func(*Loader) error) { //nolint
+func openDB(t *testing.T, dialect, connStr string) *sql.DB { //nolint:unused
+	t.Helper()
 	db, err := sql.Open(dialect, connStr)
 	if err != nil {
 		t.Errorf("failed to open database: %v", err)
-		return
 	}
-	defer db.Close()
+	t.Cleanup(func() {
+		_ = db.Close()
+	})
 
 	if err := db.Ping(); err != nil {
 		t.Errorf("failed to connect to database: %v", err)
-		return
 	}
+	return db
+}
 
+func loadSchemaInOneQuery(t *testing.T, db *sql.DB, schemaFilePath string) { //nolint:unused
+	t.Helper()
 	schema, err := os.ReadFile(schemaFilePath)
 	if err != nil {
 		t.Errorf("cannot read schema file: %v", err)
 		return
 	}
-	helper, err := helperForDialect(dialect)
+	loadSchemaInBatches(t, db, [][]byte{schema})
+}
+
+func loadSchemaInBatchesBySplitter(t *testing.T, db *sql.DB, schemaFilePath string, splitter []byte) { //nolint:unused
+	t.Helper()
+	schema, err := os.ReadFile(schemaFilePath)
 	if err != nil {
-		t.Errorf("cannot get helper: %v", err)
-		return
-	}
-	if err := helper.init(db); err != nil {
-		t.Errorf("cannot init helper: %v", err)
+		t.Errorf("cannot read schema file: %v", err)
 		return
 	}
+	batches := bytes.Split(schema, splitter)
+	loadSchemaInBatches(t, db, batches)
+}
 
-	var batches [][]byte
-	if h, ok := helper.(batchSplitter); ok {
-		batches = append(batches, bytes.Split(schema, h.splitter())...)
-	} else {
-		batches = append(batches, schema)
-	}
-
+func loadSchemaInBatches(t *testing.T, db *sql.DB, batches [][]byte) { //nolint:unused
+	t.Helper()
 	for _, b := range batches {
 		if len(b) == 0 {
 			continue
 		}
-		if _, err = db.Exec(string(b)); err != nil {
+		if _, err := db.Exec(string(b)); err != nil {
 			t.Errorf("cannot load schema: %v", err)
 			return
 		}
 	}
+}
 
+func testLoader(t *testing.T, db *sql.DB, dialect string, additionalOptions ...func(*Loader) error) { //nolint:unused
 	t.Run("LoadFromDirectory", func(t *testing.T) {
 		options := append(
 			[]func(*Loader) error{
@@ -524,18 +531,18 @@ func testLoader(t *testing.T, dialect, connStr, schemaFilePath string, additiona
 		// sequence issues.
 
 		var sql string
-		switch helper.paramType() {
-		case paramTypeDollar:
+		switch dialect {
+		case "postgres", "pgx", "clickhouse":
 			sql = "INSERT INTO posts (title, content, created_at, updated_at) VALUES ($1, $2, $3, $4)"
-		case paramTypeQuestion:
+		case "mysql", "sqlite3", "mssql":
 			sql = "INSERT INTO posts (title, content, created_at, updated_at) VALUES (?, ?, ?, ?)"
-		case paramTypeAtSign:
+		case "sqlserver", "spanner":
 			sql = "INSERT INTO posts (title, content, created_at, updated_at) VALUES (@p1, @p2, @p3, @p4)"
 		default:
-			panic("unrecognized param type")
+			t.Fatalf("undefined param type for %s dialect, modify switch statement", dialect)
 		}
 
-		_, err = db.Exec(sql, "Post title", "Post content", time.Now(), time.Now())
+		_, err := db.Exec(sql, "Post title", "Post content", time.Now(), time.Now())
 		if err != nil {
 			t.Errorf("cannot insert post: %v", err)
 		}
@@ -553,7 +560,7 @@ func assertFixturesLoaded(t *testing.T, l *Loader) { //nolint
 
 func assertCount(t *testing.T, l *Loader, table string, expectedCount int) { //nolint
 	count := 0
-	sql := fmt.Sprintf("SELECT COUNT(*) FROM %s", l.helper.quoteKeyword(table))
+	sql := fmt.Sprintf("SELECT COUNT(*) FROM %s", table)
 
 	row := l.db.QueryRow(sql)
 	if err := row.Scan(&count); err != nil {