Braintree\Configuration::getMerchantId PHP Method

    public function getMerchantId()
    {
        return $this->_merchantId;
    }

 public function testConstructWithArrayOfCredentials()
 {
     $config = new Braintree\Configuration(['environment' => 'sandbox', 'merchantId' => 'sandbox_merchant_id', 'publicKey' => 'sandbox_public_key', 'privateKey' => 'sandbox_private_key']);
     $this->assertEquals('sandbox', $config->getEnvironment());
     $this->assertEquals('sandbox_merchant_id', $config->getMerchantId());
 }