BaseType.php

<?php

abstract class BaseType
{
	abstract public function calculate($foo, $bar);
	
	public function validate($baz)
	{
		return $baz === true;
	}
}

SpeciaType.php

<?php

class SpecialType extends BaseType
{
	public function calculate($foo, $bar) {
		// ...
	}
}

What’s the general recommendation on testing methods in an abstract class?

Option 1: Extend BaseType just for testing. Seems weird.
Option 2: Test BaseType as part of the SpecialType test case. Seems fragile.
Option 3: Erm. Something else?