New Twiddle

controllers.application\.js

import Controller from '@ember/controller';
import { action } from '@ember/object';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
  cities = ['Barcelonaaaa', 'London', 'New York', 'Porto']
  destination = 'Barcelonaaaa'

  @action
  chooseDestination(city) {
    this.set('destination', city);
  }
}

styles.app\.css

body {
  font-size: 1rem;
  font-weight: 400;
  line-height: 1.5;
  color: #212529;
  text-align: left;
}

.container {
  align-items: baseline!important;
  display: flex!important;
  overflow-wrap:break-word;
  word-wrap: break-word;
}

.font-weight-bold {
  font-weight: 700!important;
}

.form-group {
   margin-bottom: 1rem;
}

.mb-1{
  margin-bottom: .25rem!important;
}

.ember-basic-dropdown,.ember-basic-dropdown-content,.ember-basic-dropdown-content *,.ember-power-select-dropdown * {
    box-sizing: border-box
}

.ember-power-select-trigger[dir=rtl] .ember-power-select-multiple-option,.ember-power-select-trigger[dir=rtl] .ember-power-select-trigger-multiple-input,.fa-pull-right {
    float: right
}

.ember-power-select-trigger,.ember-power-select-trigger--active,.ember-power-select-trigger:focus {
    border-top: 1px solid #aaa;
    border-bottom: 1px solid #aaa;
    border-right: 1px solid #aaa;
    border-left: 1px solid #aaa
}

.ember-power-select-trigger {
    position: relative;
    border-radius: 4px;
    background-color: #fff;
    line-height: 1.75;
    overflow-x: hidden;
    text-overflow: ellipsis;
    min-height: 1.75em;
    user-select: none;
    -webkit-user-select: none;
    color: inherit
}

.ember-power-select-trigger:after {
    content: "";
    display: table;
    clear: both
}

.ember-power-select-trigger--active,.ember-power-select-trigger:focus {
    box-shadow: none
}

.ember-basic-dropdown-trigger--below.ember-power-select-trigger[aria-expanded=true],.ember-basic-dropdown-trigger--in-place.ember-power-select-trigger[aria-expanded=true] {
    border-bottom-left-radius: 0;
    border-bottom-right-radius: 0
}

.ember-basic-dropdown-trigger--above.ember-power-select-trigger[aria-expanded=true] {
    border-top-left-radius: 0;
    border-top-right-radius: 0
}

.ember-power-select-placeholder {
    color: #999;
    display: block;
    overflow-x: hidden;
    white-space: nowrap;
    text-overflow: ellipsis
}

.ember-power-select-status-icon {
    position: absolute;
    display: inline-block;
    width: 0;
    height: 0;
    top: 0;
    bottom: 0;
    margin: auto;
    border-style: solid;
    border-width: 7px 4px 0;
    border-color: #aaa transparent transparent;
    right: 5px
}

.ember-basic-dropdown-trigger[aria-expanded=true] .ember-power-select-status-icon {
    transform: rotate(180deg)
}

.ember-power-select-clear-btn {
    position: absolute;
    cursor: pointer;
    right: 25px
}

.ember-power-select-trigger-multiple-input {
    font-family: inherit;
    font-size: inherit;
    border: none;
    display: inline-block;
    line-height: inherit;
    -webkit-appearance: none;
    outline: 0;
    padding: 0;
    float: left;
    background-color: transparent;
    text-indent: 2px
}

.ember-power-select-trigger-multiple-input:disabled {
    background-color: #eee
}

.ember-power-select-trigger-multiple-input::placeholder {
    opacity: 1;
    color: #999
}

.ember-power-select-trigger-multiple-input::-webkit-input-placeholder {
    opacity: 1;
    color: #999
}

.ember-power-select-trigger-multiple-input::-moz-placeholder {
    opacity: 1;
    color: #999
}

.ember-power-select-trigger-multiple-input::-ms-input-placeholder {
    opacity: 1;
    color: #999
}

.ember-power-select-multiple-options {
    padding: 0;
    margin: 0
}

.ember-power-select-multiple-option {
    border: 1px solid gray;
    border-radius: 4px;
    color: #333;
    background-color: #e4e4e4;
    padding: 0 4px;
    display: inline-block;
    line-height: 1.45;
    float: left;
    margin: 2px 0 2px 3px
}

.ember-power-select-multiple-remove-btn {
    cursor: pointer
}

.ember-power-select-multiple-remove-btn:not(:hover) {
    opacity: .5
}

.ember-power-select-search {
    padding: 4px
}

.ember-power-select-search-input {
    border: 1px solid #aaa;
    border-radius: 0;
    width: 100%;
    font-size: inherit;
    line-height: inherit;
    padding: 0 5px
}

.ember-power-select-search-input:focus {
    border: 1px solid #aaa;
    box-shadow: none
}

.ember-power-select-dropdown {
    border-left: 1px solid #aaa;
    border-right: 1px solid #aaa;
    line-height: 1.75;
    border-radius: 4px;
    box-shadow: none;
    overflow: hidden;
    color: inherit
}

.ember-power-select-dropdown.ember-basic-dropdown-content--above {
    border-top: 1px solid #aaa;
    border-bottom: none;
    border-bottom-left-radius: 0;
    border-bottom-right-radius: 0
}

.ember-power-select-dropdown.ember-basic-dropdown-content--below,.ember-power-select-dropdown.ember-basic-dropdown-content--in-place {
    border-top: none;
    border-bottom: 1px solid #aaa;
    border-top-left-radius: 0;
    border-top-right-radius: 0
}

.ember-power-select-dropdown.ember-basic-dropdown-content--in-place {
    width: 100%
}

.ember-power-select-options {
    list-style: none;
    margin: 0;
    padding: 0;
    user-select: none;
    -webkit-user-select: none
}

.ember-power-select-options[role=listbox] {
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    max-height: 12.25em
}

.ember-power-select-option {
    cursor: pointer;
    padding: 0 8px
}

.ember-power-select-group[aria-disabled=true] {
    color: #999;
    cursor: not-allowed
}

.ember-power-select-group[aria-disabled=true] .ember-power-select-option,.ember-power-select-option[aria-disabled=true] {
    color: #999;
    pointer-events: none;
    cursor: not-allowed
}

.ember-power-select-option[aria-selected=true] {
    background-color: #ddd
}

.ember-power-select-option[aria-current=true] {
    background-color: #5897fb;
    color: #fff
}

.ember-power-select-group-name {
    cursor: default;
    font-weight: 700
}

.ember-power-select-trigger[aria-disabled=true] {
    background-color: #eee
}

.ember-power-select-trigger {
    padding: 0 16px 0 0
}

.ember-power-select-placeholder,.ember-power-select-selected-item {
    margin-left: 8px
}

.ember-power-select-group .ember-power-select-group .ember-power-select-group-name {
    padding-left: 24px
}

.ember-power-select-group .ember-power-select-group .ember-power-select-option {
    padding-left: 40px
}

.ember-power-select-group .ember-power-select-option {
    padding-left: 24px
}

.ember-power-select-group .ember-power-select-group-name {
    padding-left: 8px
}

.ember-power-select-trigger[dir=rtl] {
    padding: 0 0 0 16px
}

.ember-power-select-trigger[dir=rtl] .ember-power-select-placeholder,.ember-power-select-trigger[dir=rtl] .ember-power-select-selected-item {
    margin-right: 8px
}

.ember-power-select-trigger[dir=rtl] .ember-power-select-status-icon {
    left: 5px;
    right: initial
}

.ember-power-select-trigger[dir=rtl] .ember-power-select-clear-btn {
    left: 25px;
    right: initial
}

.ember-power-select-dropdown[dir=rtl] .ember-power-select-group .ember-power-select-group .ember-power-select-group-name {
    padding-right: 24px
}

.ember-power-select-dropdown[dir=rtl] .ember-power-select-group .ember-power-select-group .ember-power-select-option {
    padding-right: 40px
}

.ember-power-select-dropdown[dir=rtl] .ember-power-select-group .ember-power-select-option {
    padding-right: 24px
}

.ember-power-select-dropdown[dir=rtl] .ember-power-select-group .ember-power-select-group-name {
    padding-right: 8px
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
<div class="container">
<div class="form-group        font-weight-bold mb-1" data-test-transfer-type="">
<PowerSelect @matchTriggerWidth={{false}} @renderInPlace={{true}} @selected={{this.destination}} @options={{this.cities}} @onChange={{this.chooseDestination}} as |name|>
  {{name}}
</PowerSelect>
</div>
</div>
<br>
<br>

tests.test-helper\.js

import Application from '../app';
import config from '../config/environment';
import { setApplication } from '@ember/test-helpers';
import { assign } from '@ember/polyfills';
import { start } from 'ember-qunit';

let attributes = {
  rootElement: '#test-root',
  autoboot: false
};
attributes = assign(attributes, config.APP);

let application = Application.create(attributes);
setApplication(application);

start();

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0",
    "ember-power-select" : "4.1.0"
  }
}