Added testing framework and updated dependencies.

src/components/HelloWorld.test.ts

@@ -0,0 +1,14 @@
+import "jest";
+import {shallowMount} from "@vue/test-utils";
+import HelloWorld from "../components/HelloWorld.vue";
+
+describe("HelloWorld.vue", () => {
+  test("renders props.msg when passed", () => {
+    const msg = "new message"
+    const wrapper = shallowMount(HelloWorld, {
+      propsData: { msg }
+    });
+
+    expect(wrapper.text()).toMatch(msg)
+  });
+});