serialize payment request for signature

lib/PayPro.js

@@ -167,6 +167,15 @@ PayPro.prototype.setObj = function(obj) {
   return this;
 };
 
+PayPro.prototype.serializeForSig = function() {
+  if (this.messageType !== 'PaymentRequest')
+    throw new Error('serializeForSig is only for PaymentRequest');
+
+  this.message.set('signature', new Buffer([]));
+  var buf = this.serialize();
+  return buf;
+};
+
 PayPro.prototype.serialize = function() {
   //protobufjs returns either a Buffer or an ArrayBuffer
   //but we always want a Buffer (which browserify understands, browser or no)

test/test.PayPro.js

@@ -177,6 +177,22 @@ describe('PayPro', function() {
 
   });
 
+  describe('#serializeForSig', function() {
+
+    it('should serialize a PaymentRequest and not fail', function() {
+      var pd = new PayPro.PaymentDetails();
+      pd.set('time', 0);
+      var pdbuf = pd.toBuffer();
+
+      var paypro = new PayPro();
+      paypro.makePaymentRequest();
+      paypro.set('serialized_payment_details', pdbuf);
+      var buf = paypro.serializeForSig();
+      buf.length.should.be.greaterThan(0);
+    });
+
+  });
+
   describe('#serialize', function() {
 
     it('should serialize', function() {