test: add test for Q9

Author: webfansplz

questions/9-dependency-injection/index.test.ts

@@ -0,0 +1,11 @@
+import { mount } from "@vue/test-utils"
+import { describe, it, expect } from "vitest"
+
+import App from "./App.vue"
+
+describe("Dependency Injection", () => {
+  it("should work'", () => {
+    const wrapper = mount(App)
+    expect(wrapper.vm.$el.textContent).toBe("1")
+  })
+})