test(runtime-core): test app API warnings (#2079)

Author: edison1105

packages/runtime-core/__tests__/apiCreateApp.spec.ts

@@ -58,6 +58,11 @@ describe('api: createApp', () => {
 
     const root = nodeOps.createElement('div')
     const app = createApp(Comp)
+
+    // warning
+    app.unmount(root)
+    expect(`that is not mounted`).toHaveBeenWarned()
+
     app.mount(root)
 
     app.unmount(root)
@@ -92,6 +97,11 @@ describe('api: createApp', () => {
     app.mount(root)
     expect(serializeInner(root)).toBe(`3,2`)
     expect('[Vue warn]: injection "__proto__" not found.').toHaveBeenWarned()
+
+    const app2 = createApp(Root)
+    app2.provide('bar', 1)
+    app2.provide('bar', 2)
+    expect(`App already provides property with key "bar".`).toHaveBeenWarned()
   })
 
   test('component', () => {