test: prevent plugin install twice

src/browser.js

@@ -13,7 +13,6 @@ function install(Vue, options = {}) {
   if (Vue.__vuemeta_installed) {
     return
   }
-
   Vue.__vuemeta_installed = true
 
   options = setOptions(options)

src/index.js

@@ -12,7 +12,6 @@ function install(Vue, options = {}) {
   if (Vue.__vuemeta_installed) {
     return
   }
-
   Vue.__vuemeta_installed = true
 
   options = setOptions(options)

test/unit/plugin-browser.test.js

@@ -65,6 +65,18 @@ describe('plugin', () => {
     expect(VueMetaBrowserPlugin.version).toBe('test-version')
   })
 
+  test('plugin isnt be installed twice', () => {
+    expect(Vue.__vuemeta_installed).toBe(true)
+
+    Vue.prototype.$meta = undefined
+    Vue.use({ ...VueMetaBrowserPlugin })
+
+    expect(Vue.prototype.$meta).toBeUndefined()
+
+    // reset Vue
+    Vue = loadVueMetaPlugin(true)
+  })
+
   test('updates can be paused and resumed', async () => {
     const { batchUpdate: _batchUpdate } = jest.requireActual('../../src/client/update')
     const batchUpdateSpy = batchUpdate.mockImplementation(_batchUpdate)

test/unit/plugin-server.test.js

@@ -63,6 +63,18 @@ describe('plugin', () => {
     expect(VueMetaServerPlugin.version).toBe('test-version')
   })
 
+  test('plugin isnt be installed twice', () => {
+    expect(Vue.__vuemeta_installed).toBe(true)
+
+    Vue.prototype.$meta = undefined
+    Vue.use({ ...VueMetaServerPlugin })
+
+    expect(Vue.prototype.$meta).toBeUndefined()
+
+    // reset Vue
+    Vue = loadVueMetaPlugin(true)
+  })
+
   test('prints deprecation warning once when using _hasMetaInfo', () => {
     const warn = jest.spyOn(console, 'warn').mockImplementation(() => {})