       length: 5
       expected:
         '<div>
-          <b>123</b>
-          <i>456</i>
-        </div>
-        <div>
-          <b>
+          <#>123</#>
+          <i>456</i>
+        </div>
+        <div>
+          <#>
             <s>7</s>
             <u>8</u>
             <s>9</s>
             <u>0</u>
-          </b>
+          </#>
         </div>
         <div>
           <b>abcdefg</b>

      length: 6
      expected:
        '<div>
          <b>123</b>
          <b>
            <i>456</i>
          </b>
        </div>
        <div>
          <b>
            <s>7</s>
            <u>8</u>
          </b>
          <s>9</s>
          <u>0</u>
        </div>

      length: 5
      expected:
        '<div>
          <#>123</#>
          <i>456</i>
        </div>
        <div>
          <#>
            <s>7</s>
            <u>8</u>
            <s>9</s>
            <u>0</u>
          </#>
        </div>
        <div>
          <b>abcdefg</b>
