public function testFlattenWithDepth()
{
// No depth flattens recursively
$c = new Collection([['#foo', ['#bar', ['#baz']]], '#zap']);
$this->assertEquals(['#foo', '#bar', '#baz', '#zap'], $c->flatten()->all());
// Specifying a depth only flattens to that depth
$c = new Collection([['#foo', ['#bar', ['#baz']]], '#zap']);
$this->assertEquals(['#foo', ['#bar', ['#baz']], '#zap'], $c->flatten(1)->all());
$c = new Collection([['#foo', ['#bar', ['#baz']]], '#zap']);
$this->assertEquals(['#foo', '#bar', ['#baz'], '#zap'], $c->flatten(2)->all());
}