test: improve tests and typing for runtime-core (#100)

* test: add test case for declaring Array prop type with constructor casting in `createComponent`

* test: add test case for `setup(props)` with explicit props declaration

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

@@ -74,6 +74,39 @@ describe('api: setup context', () => {
     expect(dummy).toBe(1)
   })
 
+  it('setup props should resolve the correct types from props object', async () => {
+    const count = ref(0)
+    let dummy
+
+    const Parent = {
+      render: () => h(Child, { count: count.value })
+    }
+
+    const Child = createComponent({
+      props: {
+        count: Number
+      },
+
+      setup(props) {
+        watch(() => {
+          dummy = props.count
+        })
+        return () => h('div', props.count)
+      }
+    })
+
+    const root = nodeOps.createElement('div')
+    render(h(Parent), root)
+    expect(serializeInner(root)).toMatch(`<div>0</div>`)
+    expect(dummy).toBe(0)
+
+    // props should be reactive
+    count.value++
+    await nextTick()
+    expect(serializeInner(root)).toMatch(`<div>1</div>`)
+    expect(dummy).toBe(1)
+  })
+
   it('context.attrs', async () => {
     const toggle = ref(true)