 factors:
</p>
	<ul>
		<li><b>Size</b><br>
		For collections (<code>strings, lists, tuples, dictionaries</code>) test with:
		<ul>
			<li>empty collection
			<li>a collection with 1 item
			<li>smallest interesting case
			<li>collection with several items		
		</ul>
		<li><b>Dichotomies</b><br>
			Consider your situation:<br>
		<br>
		For example:
		<ul>
			<li>vowels/non-vowels
			<li>even/odd
			<li>positive/negative
			<li>empty/full
			<li>etc.
		</ul>
		<li><b>Boundaries</b><br>
			If a function behave