fix checkMerge, and tests

lib/TransactionBuilder.js

@@ -866,8 +866,13 @@ TransactionBuilder.fromObj = function(data) {
 
 
 TransactionBuilder.prototype._checkMergeability = function(b) {
-  if (JSON.stringify(this.vanilla) !== JSON.stringify(this.vanilla))
-    throw new Error('cannot merge: incompatible builders')
+
+  var toCompare = ['opts', 'hashToScriptMap', 'outs', 'uxtos'];
+  for (var i in toCompare) {
+    var k = toCompare[i];
+    if (JSON.stringify(this.vanilla[k]) !== JSON.stringify(b.vanilla[k]))
+      throw new Error('cannot merge: incompatible builders:' + k)
+  }
 };
 
 // TODO this could be on Script class

test/test.TransactionBuilder.js

@@ -1030,7 +1030,7 @@ describe('TransactionBuilder', function() {
       }]);
       (function() {
         b2.merge(b);
-      }).should.throw('NTXID');
+      }).should.throw('incompatible');
     });
     it('should check addresses', function() {
       // bad out
@@ -1040,7 +1040,7 @@ describe('TransactionBuilder', function() {
       }]);
       (function() {
         b2.merge(b);
-      }).should.throw('NTXID');
+      }).should.throw('incompatible');
     });
 
 
@@ -1060,7 +1060,7 @@ describe('TransactionBuilder', function() {
 
       (function() {
         b2.merge(b);
-      }).should.throw('signhash');
+      }).should.throw('incompatible');
     });
 
 
@@ -1202,7 +1202,7 @@ describe('TransactionBuilder', function() {
       b2.sign(k2);
       (function() {
         b2.merge(b)
-      }).should.throw('NTXID');
+      }).should.throw('incompatible');
     });