<button>
  <span>бесплатная диагностика</span>
  <svg width="200" height="80">
    <path d="M10,10 190,10 190,70 10,70z" />
  </svg>
</button>

button {
  width: 200px;
  height: 80px;
  
}
svg{
  position: absolute;
  top: 10px;
  left: 10px;
  width:  inherit;
  height: inherit;
  fill: none;
  sroke-width: 2px;
  stroke: #000;
  stroke-dasharray:130 80;
  transition: 0.68s linear;
}

button:focus svg{
  stroke-dasharray:1000 80;
  stroke: #fff;
}