diff --git a/internal/db/db_test.go b/internal/db/db_test.go
index 42c9bfc..4c127ca 100644
--- a/internal/db/db_test.go
+++ b/internal/db/db_test.go
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"io"
 	"log/slog"
+	"os"
 	"path/filepath"
 	"testing"
 )
@@ -124,13 +125,22 @@ func TestOpen_BlankPath_异常(t *testing.T) {
 	}
 }
 
-func TestOpen_MissingParentDir_异常(t *testing.T) {
+func TestOpen_CreatesParentDir_正常(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 
-	// Parent directory does not exist, so the connection cannot be established.
-	path := filepath.Join(t.TempDir(), "does-not-exist", "cyrene.db")
-	if _, err := Open(ctx, path, testLogger()); err == nil {
-		t.Fatalf("Open(%q) expected error for missing parent dir, got nil", path)
+	// Parent directory does not exist yet: Open must create it so a custom
+	// DATA_DIR works on first run.
+	dir := filepath.Join(t.TempDir(), "does-not-exist")
+	path := filepath.Join(dir, "cyrene.db")
+	db, err := Open(ctx, path, testLogger())
+	if err != nil {
+		t.Fatalf("Open(%q) error creating parent dir: %v", path, err)
+	}
+	defer db.Close()
+	if fi, err := os.Stat(dir); err != nil {
+		t.Fatalf("parent dir not created: %v", err)
+	} else if !fi.IsDir() {
+		t.Fatalf("parent path is not a dir: %v", fi)
 	}
 }