Solve language display problem in result playlist. problem was in the mirage serializer definition
import { isChecked } from 'app-client/helpers/is-checked';
import { module, test } from 'qunit';
module('Unit | Helper | is checked');
// Replace this with your real tests.
test('it works', function(assert) {
let result = isChecked([42]);
assert.ok(result);
});