<!doctype html>
<title>CSS Test Reference</title>
<style>
  .container, .not_a_container {
    width: auto;
    height: 100px;
    border: 1px solid black;
    margin-bottom: 10px;
  }
  span {
    border: 1px solid green;
    margin: 2px;
  }
</style>
<div style="width:150px">
  <div class=container>
    <main>
      <div style="display:flex">
        <span style="flex:1">Test1</span>
        <span style="flex:1">Test2</span>
        <span style="flex:1">Test3</span>
      </div>
    </main>
  </div>
</div>
<div style="width:200px">
  <div class=container>
    <main>
      <div>
        <span style="display:block">Test1</span>
        <span style="display:block">Test2</span>
        <span style="display:block">Test3</span>
      </div>
    </main>
  </div>
</div>
<div style="width:150px">
  <div class=not_a_container>
    <main>
      <div>
        <span>Test1</span>
        <span>Test2</span>
        <span>Test3</span>
      </div>
    </main>
  </div>
</div>
