test: add tests for new functionalities

src/client/updaters/attribute.js

@@ -43,8 +43,6 @@ export default function updateAttribute (appId, { attribute } = {}, type, attrs,
       if (attrs[attr]) {
         data[attr] = data[attr] || {}
         data[attr][appId] = attrs[attr]
-      } else {
-        delete data[attr][appId]
       }
     }
   }

src/index.js

@@ -28,6 +28,6 @@ function install (Vue, options = {}) {
 export default {
   version,
   install,
-  generate: process.server ? generate : () => showWarningNotSupportedInBrowserBundle('generate'),
+  generate: metaInfo => process.server ? generate(metaInfo) : showWarningNotSupportedInBrowserBundle('generate'),
   hasMetaInfo
 }

src/server/generateServerInjector.js

@@ -58,13 +58,15 @@ export default function generateServerInjector (options, metaInfo) {
             }
           }
 
-          for (const appId in serverInjector.extraData) {
-            const data = serverInjector.extraData[appId][type]
-            if (data) {
-              for (const attr in data) {
-                attributeData[attr] = {
-                  ...attributeData[attr],
-                  [appId]: data[attr]
+          if (serverInjector.extraData) {
+            for (const appId in serverInjector.extraData) {
+              const data = serverInjector.extraData[appId][type]
+              if (data) {
+                for (const attr in data) {
+                  attributeData[attr] = {
+                    ...attributeData[attr],
+                    [appId]: data[attr]
+                  }
                 }
               }
             }

src/shared/mixin.js

@@ -155,6 +155,7 @@ export default function createMixin (Vue, options) {
       // Wait that element is hidden before refreshing meta tags (to support animations)
       const interval = setInterval(() => {
         if (this.$el && this.$el.offsetParent !== null) {
+          /* istanbul ignore next line */
           return
         }