public function test_createdAt()
 {
     $customer = Braintree\Customer::createNoValidate();
     $past = clone $customer->createdAt;
     $past->modify("-1 hour");
     $future = clone $customer->createdAt;
     $future->modify("+1 hour");
     $collection = Braintree\Customer::search(array(Braintree\CustomerSearch::id()->is($customer->id), Braintree\CustomerSearch::createdAt()->between($past, $future)));
     $this->assertEquals(1, $collection->maximumCount());
     $this->assertEquals($customer->id, $collection->firstItem()->id);
     $collection = Braintree\Customer::search(array(Braintree\CustomerSearch::id()->is($customer->id), Braintree\CustomerSearch::createdAt()->lessThanOrEqualTo($future)));
     $this->assertEquals(1, $collection->maximumCount());
     $this->assertEquals($customer->id, $collection->firstItem()->id);
     $collection = Braintree\Customer::search(array(Braintree\CustomerSearch::id()->is($customer->id), Braintree\CustomerSearch::createdAt()->greaterThanOrEqualTo($past)));
     $this->assertEquals(1, $collection->maximumCount());
     $this->assertEquals($customer->id, $collection->firstItem()->id);
 }