const items = [{ id: 'a' }, { id: 'b' }]; export default { skip_if_ssr: true, get props() { return { foo: 'b', items }; }, test({ assert, component, target }) { const options = target.querySelectorAll('option'); assert.equal(options[0].selected, false); assert.equal(options[1].selected, true); component.foo = items[0].id; assert.equal(options[0].selected, true); assert.equal(options[1].selected, false); } };