each yield test

components.x-list-item.js

import Ember from 'ember';

export default Ember.Component.extend({
  tagName: 'li',
});

components.x-list.js

import Ember from 'ember';

export default Ember.Component.extend({
  tagName: 'ul',
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  items: ["one", "two", "three"],
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{#x-list items=items as |listItem|}}
  {{listItem}}
  {{#listItem as |item|}}Item: {{item}}{{/listItem}}
{{/x-list}}
<br>
<br>

templates.components.x-list-item.hbs

{{#if has-block}}
  {{yield item}}
{{else}}
  {{item}}
{{/if}}

templates.components.x-list.hbs

{{#each items as |item|}}
  {{yield (component 'x-list-item' item=item)}}
{{/each}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}