old_contents: import Ember from 'ember';
  import { moduleForComponent, test } from 'ember-qunit';
  
  moduleForComponent( 'sl-panel', 'Unit - component: sl-panel' );
  
  test( 'Default classes are present', function( assert ) {
      let $component = this.render();
  
      assert.ok(
          $component.hasClass( 'panel' ),
          'Default rendered component has class "panel"'
      );
  
      assert.ok(
          $component.hasClass( 'panel-default' ),
          'Default rendered component has class "panel-default"'
      );
  
      assert.ok(
          $component.hasClass( 'sl-panel' ),
          'Default rendered component has class "sl-panel"'
      );
  });
  
  test( 'Loading state applies class name', function( assert ) {
      let component  = this.subject(),
          $component = this.render();
  
      assert.strictEqual(
          $component.hasClass( 'sl-loading' ),
          false,
          'Default rendered component does not have class "sl-loading"'
      );
  
      Ember.run( () => {
          component.set( 'loading', true );
      });
  
      assert.ok(
          $component.hasClass( 'sl-loading' ),
          'Rendered component has class "sl-loading"'
      );
  });
  
  test( 'Valid heading value renders panel-heading', function( assert ) {
      let component  = this.subject(),
          $component = this.render();
  
      assert.strictEqual(
          $component.find( '.panel-heading' ).length,
          0,
          'Default rendered component has no .panel-heading'
      );
  
      Ember.run( () => {
          component.set( 'heading', 'Test' );
      });
  
      assert.strictEqual(
          $component.find( '.panel-heading' ).length,
          1,
          'Rendered component has panel-heading text'
      );
  });
  
new_contents: import Ember from 'ember';
  import { moduleForComponent, test } from 'ember-qunit';
  
  moduleForComponent( 'sl-panel', 'Unit - component: sl-panel' );
  
  test( 'Default classes are present', function( assert ) {
      var $component = this.render();
  
      assert.ok(
          $component.hasClass( 'panel' ),
          'Default rendered component has class "panel"'
      );
  
      assert.ok(
          $component.hasClass( 'panel-default' ),
          'Default rendered component has class "panel-default"'
      );
  
      assert.ok(
          $component.hasClass( 'sl-panel' ),
          'Default rendered component has class "sl-panel"'
      );
  });
  
  test( 'Loading state applies class name', function( assert ) {
      var component  = this.subject(),
          $component = this.render();
  
      assert.strictEqual(
          $component.hasClass( 'sl-loading' ),
          false,
          'Default rendered component does not have class "sl-loading"'
      );
  
      Ember.run( () => {
          component.set( 'loading', true );
      });
  
      assert.ok(
          $component.hasClass( 'sl-loading' ),
          'Rendered component has class "sl-loading"'
      );
  });
  
  test( 'Valid heading value renders panel-heading', function( assert ) {
      var component  = this.subject(),
          $component = this.render();
  
      assert.strictEqual(
          $component.find( '.panel-heading' ).length,
          0,
          'Default rendered component has no .panel-heading'
      );
  
      Ember.run( () => {
          component.set( 'heading', 'Test' );
      });
  
      assert.strictEqual(
          $component.find( '.panel-heading' ).length,
          1,
          'Rendered component has panel-heading text'
      );
  });
  
subject: Revert assignments back to "var" from "let"