chores: add test for useCssModule.

Author: Trendymen

test/apis/useCssModule.spec.js

@@ -0,0 +1,31 @@
+const Vue = require('vue/dist/vue.common.js')
+const { useCSSModule } = require('../../src')
+
+const style = { whateverStyle: 'whateverStyle' }
+
+function injectStyles() {
+  Object.defineProperty(this, '$style', {
+    configurable: true,
+    get: function () {
+      return style
+    },
+  })
+}
+
+describe('api/useCssModule', () => {
+  it('should get the same object', (done) => {
+    const vm = new Vue({
+      beforeCreate() {
+        injectStyles.call(this)
+      },
+      template: '<div>{{style}}</div>',
+      setup() {
+        const style = useCSSModule()
+        return { style }
+      },
+    })
+    vm.$mount()
+    expect(vm.style).toBe(style)
+    done()
+  })
+})