fix(core): string walk api test error

package.json

@@ -1,6 +1,6 @@
 {
   "scripts": {
-    "prepublishOnly": "lerna run build",
+    "prepublishOnly": "npm run test",
     "bootstrap": "lerna bootstrap",
     "publish-all": "lerna publish --conventional-commits --registry=https://registry.npmjs.org/",
     "test": "lerna run build && lerna run link && lerna run test",

packages/bbob-core/test/index.test.js

@@ -78,6 +78,7 @@ describe('@bbob/core', () => {
           'Large',
           ' ',
           'Text',
+          ' ',
           {
             tag: 'test-tag',
             attrs: {},