tests/linear_gradient_rect.svg

<svg viewBox="0 0 10 10" xmlns="http://www.w3.org/2000/svg"
     xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <linearGradient id="grad1">
      <!-- % and number -->
      <stop offset="10%"  stop-color="blue" />
      <stop offset="0.9" stop-color="cyan" stop-opacity="0.8" />
    </linearGradient>
  </defs>
  <rect x="2" y="2" width="6" height="2" fill="url(#grad1)" />
</svg>