feat: defineModel 增加默认值示例及测试

pages/composition-api/basic/define-model/Foo.uvue

@@ -2,6 +2,7 @@
   <view>
     <text id="model-value-text">modelValue in Foo: {{modelValue}}</text>
     <text class='uni-common-mt' id="msg-text">msg in Foo: {{msg}}</text>
+    <text class='uni-common-mt' id="default-num-text">num: {{defaultNum}}</text>
     <button class='uni-common-mt' id="update-value-btn" @click='updateValue'>update value</button>
   </view>
 </template>
@@ -11,7 +12,8 @@
   const modelValue = defineModel({ type: String })
 
   // 在被修改时，触发 "update:msg" 事件
-  const msg = defineModel('msg', { type: String })
+  const msg = defineModel('msg', { type: String, default: 'default msg' })
+  const defaultNum = defineModel('num', { type: Number, default: 10 })
 
   const updateValue = () => {
     modelValue.value += '1'

pages/composition-api/basic/define-model/define-model.test.js

@@ -23,6 +23,9 @@ describe('defineModel', () => {
     const msgText = await page.$('#msg-text')
     expect(await msgText.text()).toBe('msg in Foo: msg')
     
+    const defaultNumText = await page.$('#default-num-text')
+    expect(await defaultNumText.text()).toBe('num: 10')
+
     const msgInput = await page.$('#msg-input')
     expect(await msgInput.property('value')).toBe('msg')