public function test_fails()
 {
     $c = new Collection([['id' => 1, 'name' => 'Hello'], ['id' => 2, 'name' => 'World']]);
     $this->assertEquals([1 => ['id' => 2, 'name' => 'World']], $c->fails(['id' => 'in:1'])->all());
     $c = new Collection([]);
     $this->assertEquals([], $c->fails(['id' => 'in:1'])->all());
     $c = new Collection([['id' => 1, 'name' => 'Hello'], ['id' => 2, 'name' => 'World']]);
     $this->assertEquals([], $c->fails([])->all());
 }