title: why don't the ng-leave/ng-enter classes get added
body: <p>according to the angular docs
  <a href="https://docs.angularjs.org/api/ng/directive/ngRepeat#animations" rel="nofollow">https://docs.angularjs.org/api/ng/directive/ngRepeat#animations</a></p>
  
  <blockquote>
    <p>".enter - when a new item is added to the list or when an item is
    revealed after a filter</p>
    
    <p>.leave - when an item is removed from the list or when an item is
    filtered out"</p>
  </blockquote>
  
  <p>yet, when I .push({}) or .splice(-1, 1) from an array, neither of those classes are added to the ng-repeat. what's the problem?</p>
  
  <pre><code>&lt;div ng-controller="MyCtrl"&gt;
     &lt;button ng-click="addLine()"&gt;
       add
     &lt;/button&gt;
     &lt;button ng-click="removeLine()"&gt;
       remove
     &lt;/button&gt;
    &lt;div ng-repeat="line in lines"&gt;
        &lt;div class="preview"&gt;{{$index}}&lt;/div&gt;
     &lt;/div&gt;
  &lt;/div&gt;
  var myApp = angular.module('myApp', ['ngAnimate']);
  
  //myApp.directive('myDirective', function() {});
  //myApp.factory('myService', function() {});
  
  function MyCtrl($scope) {
          $scope.addLine = function(){
          $scope.lines.push({})
      }
      $scope.removeLine = function(){
          $scope.lines.splice(-1, 1)
      }
      $scope.lines = [{
          text: 'res1'},
      {
          text: 'res2'}];
  }
  </code></pre>
  
  <p><strong>as Ted noted in his answer, having actual css styles for .ng-enter / .ng-leave is required, otherwise the ngAnimate module will not add the .ng-enter classes to the DOM elements</strong></p>
  
  <p>To be more clear, I don't care about actually doing an animation right now. The issue for me here is that the .ng-enter classes don't actually get applied to the class attribute of an element unless you have css styles for .ng-enter</p>
  
  <p><strong>WORKING PLUNKER
  <a href="http://plnkr.co/edit/TqpdIy6syikBhAeb5Kw3?p=preview" rel="nofollow">http://plnkr.co/edit/TqpdIy6syikBhAeb5Kw3?p=preview</a></strong></p>