Function setup

test/apis/computed.spec.js:20–27

()

      const vm = new Vue({
        template: '<div>{{ b }}</div>',
        setup() {
          const a = ref(1)
          const b = computed(() => a.value + 1)
          return {
            a,
            b,
          }
        },
      }).$mount()
      expect(vm.b).toBe(2)
      expect(vm.$el.textContent).toBe('2')