Braintree\Gateway::customer PHP Method

    public function customer()
    {
        return new CustomerGateway($this);
    }

 public function testCreateWithAccessToken()
 {
     $credentials = Test\Braintree\OAuthTestHelper::createCredentials(['clientId' => 'client_id$development$integration_client_id', 'clientSecret' => 'client_secret$development$integration_client_secret', 'merchantId' => 'integration_merchant_id']);
     $gateway = new Braintree\Gateway(['accessToken' => $credentials->accessToken]);
     $result = $gateway->customer()->create(['firstName' => 'Mike', 'lastName' => 'Jones']);
     $this->assertEquals(true, $result->success);
     $customer = $result->customer;
     $this->assertEquals('Mike', $customer->firstName);
     $this->assertEquals('Jones', $customer->lastName);
     $this->assertNotNull($customer->merchantId);
 }