/**
* Test the Functions::combine method.
*/
public function testCombine()
{
$a = function ($value) {
return $value + 2;
};
$b = function ($value) {
return $value * 3;
};
$result = Functions::combine($a, $b);
$this->assertTrue(is_callable($result), 'Combined function should be callable.');
$this->assertEquals($result(3), 15);
}