check box value not applied under ng-if

My ng-model value is not applied to checkbox under ng-if ,though value is present . It gets updated only on double click .

<div ng-show="isTrue == true">
<label>
  <input type="checkbox" name="test1" ng-model="a.testModel[0]" ng-true-value="1" ng-false-value="0" /> Testing 1 </label>
<br />
<label>
  <input type="checkbox" name="test2" ng-model="a.testModel[1]" ng-true-value="1" ng-false-value="0" /> Testing 2</label>
<br />
<label>
  <input type="checkbox" name="test3" ng-model="a.testModel[2]" ng-true-value="1" ng-false-value="0" /> Testing 3</label>
<br />
<input type="button" ng-click="submit()" value="Submit" />

Here is the plunker link Demo