For these testing purposes I see no harm, this [helper](https://github.com/guardian/frontend/blob/master/common/app/assets/stylesheets/base/_helpers.scss#L26) we have (taken from Necloas Gallher) is the most accessible way:
```css
.h {
    position: absolute !important;
    clip: rect(1px 1px 1px 1px);
    clip: rect(1px, 1px, 1px, 1px);
}
```