public function testKeyIsEmpty() { $collection = new Collection([1 => 'test2', 0 => 'test']); $this->assertEquals(new Collection([0 => 1, 1 => 0]), $collection->keys()); $collection = new Collection(['' => 'test']); $value = $collection->keys()[0]; $this->assertTrue('' === $value); $collection = new Collection(['test']); $value = $collection->keys()->toArray()[0]; $this->assertTrue(0 === $value); }