Ion-radio checked is no work, set with ngModel

Ionic Framework
1

Default check is not work, when it is called with ngModel.

<ion-radio-group [(ngModel)]=“test”>
<ion-item>
<ion-label>A</ion-label>
<ion-radio value=“right” checked></ion-radio>
</ion-item>
<ion-item>
<ion-label>b</ion-label>
<ion-radio value=“left”></ion-radio>
</ion-item>
</ion-radio-group>

But It works fine, when remove ngModel.

<ion-radio-group [(ngModel)]=“test”>
<ion-item>
<ion-label>A</ion-label>
<ion-radio value=“right” checked></ion-radio>
</ion-item>
<ion-item>
<ion-label>b</ion-label>
<ion-radio value=“left”></ion-radio>
</ion-item>
</ion-radio-group>

2

How to make it checked along with ngModel?

3

Assign to the thing ngModel is bound to.