ng-readonly not working in angular checkbox

ng-readonly only work with input type="text"

see documentation here -https://docs.angularjs.org/api/ng/directive/ngReadonly

The HTML specification does not require browsers to preserve the values of boolean attributes such as readonly. (Their presence means true and their absence means false.) If we put an Angular interpolation expression into such an attribute then the binding information would be lost when the browser removes the attribute. The ngReadonly directive solves this problem for the readonly attribute. This complementary directive is not removed by the browser and so provides a permanent reliable place to store the binding information.

if you want to disable it use this:

<input type="checkbox" ng-disabled="true" ng-model="test" />

If you like to have it "more" visible, you can always use a little javascript trick:

<input type="checkbox" ng-model="model" onclick="return false;" />