$slots->removeSlot( 'other' );
$this->assertSame( [], $slots->getModifiedRoles() );
$this->assertSame( [ 'main', 'other' ], $slots->getRemovedRoles() );
$slots->removeSlot( 'other' );
$this->assertSame( [], $slots->getModifiedRoles() );
$this->assertSame( [ 'main', 'other' ], $slots->getRemovedRoles() );