Mutation testing

<div class="stage"><div class="title">MUTATION TEST</div><div class="canvas"><div class="code mono">age <b id="operator">≥</b> 18</div><div class="checks"><span id="check17">17: FAIL</span><span id="check18">18: PASS</span><span id="check19">19: PASS</span></div><div class="verdict" id="verdict">original passes</div></div></div>

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let mutated=false;function flip(){mutated=!mutated;document.getElementById('operator').textContent=mutated?'>':'≥';document.getElementById('check18').textContent=mutated?'18: FAIL':'18: PASS';document.getElementById('check18').classList.toggle('caught',mutated);document.getElementById('verdict').textContent=mutated?'mutant killed by age 18':'original passes'}flip();setInterval(flip,1500)