prop-test.js

import Ember from 'ember';

var sizeCheckProperty = function(size) {
    return function() {
        return (this.get('size') === size);
    }.property('size');
};

export default Ember.Component.extend({
    size: 'small',
    isSmall: sizeCheckProperty('small'),
    isMedium: sizeCheckProperty('medium'),
    isLarge: sizeCheckProperty('large')
});