<!DOCTYPE html>
<style>
  text {
    font-size: 50px;
    font-style: italic;
  }
  rect {
    stroke-width: 1px;
    stroke: green;
    fill: transparent;
  }
  #middleGlyphOverhang {
    font-family: cursive;
  }
</style>
No glyphs should extend outside the rects.<br>
<svg id="svg" width="700" height="500">
  <text id="simpleText" x="50" y="50">ffffffff</text>
  <text id="textWithSpan" x="50" y="150">ffffff<tspan>ffffff</tspan></text>
  <text id="textWithDifferentSizes" x="50" y="250"><tspan font-size="30px">ffffff</tspan><tspan font-size="80px">ffffff</tspan></text>
  <text id="rotatedText" x="50" y="350" rotate="20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380">fffffffffffffffffff</text>
  <text id="middleGlyphOverhang" x="50" y="475">'faQ'</text>
</svg>
<script>
  [simpleText, textWithSpan, textWithDifferentSizes, rotatedText, middleGlyphOverhang].forEach(function (textElement) {
    var rect = document.createElementNS('http://www.w3.org/2000/svg', 'rect');
    rect.setAttribute('x', textElement.getBBox().x);
    rect.setAttribute('y', textElement.getBBox().y);
    rect.setAttribute('width', textElement.getBBox().width);
    rect.setAttribute('height', textElement.getBBox().height);
    document.getElementById('svg').appendChild(rect);
  });
</script>