index.html

<!DOCTYPE>
<html>
<head>
  <meta charset="utf-8">
</head>

<body ng-app="registration">
  <h1>HELLO</h1>

  <div ng-controller="tabswitcher">
    <div>
      <button ng-click="tab = 1">#1</button>
      <button ng-click="tab = 2" ng-disabled="!data.tab1.valid">#2</button>
      <button ng-click="tab = 3" ng-disabled="!data.tab1.valid || !data.tab2.valid">#3</button>
      <button ng-click="tab = 4" ng-disabled="!data.tab1.valid || !data.tab2.valid || !data.tab3.valid">#4</button>
    </div>

    <div>
      <form name="registrationForm">
        <div step1 ng-show="tab == 1"></div>
        <div step2 ng-show="tab == 2"></div>
        <div step3 ng-show="tab == 3"></div>
        <div step4 ng-show="tab == 4"></div>
      </form>
    </div>
  </div>

  <script src="dist/app.js"></script>
</body>

</html>