public function testIGroup()
{
$apple = ['name' => 'Apple', 'type' => 'fruit', 'colour' => 'green', 'group' => 'food'];
$bear = ['name' => 'Bear', 'type' => 'animal', 'colour' => 'brown', 'group' => 'creature'];
$carrot = ['name' => 'Carrot', 'type' => 'vegetable', 'colour' => 'brown', 'group' => 'food'];
$list = ['a' => $apple, 'b' => $bear, 'c' => $carrot];
$expect = ['fruit' => ['a' => $apple], 'animal' => ['b' => $bear], 'vegetable' => ['c' => $carrot]];
$this->assertEquals($expect, Arrays::igroup($list, 'type'));
$expect = ['food' => ['fruit' => ['a' => $apple], 'vegetable' => ['c' => $carrot]], 'creature' => ['animal' => ['b' => $bear]]];
$this->assertEquals($expect, Arrays::igroup($list, 'group', 'type'));
$expect = ['food' => ['a' => $apple, 'c' => $carrot], 'creature' => ['b' => $bear]];
$this->assertEquals($expect, Arrays::igroup($list, 'group'));
}
