Click in the input, move to the end of the text, then tab to the button. The visible text should stay near the caret position instead of jumping back to the beginning.
After the input loses focus, input.scrollLeft remains at the same non-zero position it had before blur. This keeps the end of a long value visible.
const input = document.querySelector('input');
const button = document.querySelector('button');
input.focus();
input.scrollLeft = input.scrollWidth;
const before = input.scrollLeft;
button.focus();
assert_equals(input.scrollLeft, before);