public function testPowerSet(Set $A, Set $expected)
{
$P⟮S⟯ = $A->powerSet();
$this->assertEquals($expected, $P⟮S⟯);
$this->assertEquals($expected->asArray(), $P⟮S⟯->asArray());
$this->assertEquals(count($expected), count($P⟮S⟯));
}