How to fill input only by events?

I need to add some chars to input only by events, without access to input.value. My try:

HTML:

<input id="text" type="text">

JS:

// prepare     
let et = document.getElementById('text');
et.value = '';

// my try
et.dispatchEvent(new KeyboardEvent('keydown',  {key:'s', code:'KeyS', bubbles: true})); 
et.dispatchEvent(new KeyboardEvent('keypress', {key:'s', code:'KeyS', bubbles: true}));
et.dispatchEvent(new InputEvent('input', {}));
et.dispatchEvent(new KeyboardEvent('keyup', {key:'s', code:'KeyS', bubbles: true}));

// check
if (et.value === 's')
    alert ('success');
else 
    alert ('failure');

I have got 'failure' always. I need 'success')