CSS文字水平居中且宽度自适应

<div class="a">
    <div class="b">测试<div>
</div>


<style>
.a{
    width: 200px;
    height: 200px;
    position: relative;
}
.b{
    position: absolute;
    top: 20px;
    left: 0;
    right: 0;
    margin: auto;
    width: fit-content; //根据文字长度自适应
    background: blue;
}
</style>