check for dust before creating transaction

src/wallet.js

@@ -179,6 +179,8 @@ var Wallet = function (seed, options) {
     }
 
     this.createTx = function(to, value, fixedFee) {
+        checkDust(value)
+
         var tx = new Transaction()
         tx.addOutput(to, value)
 
@@ -206,6 +208,12 @@ var Wallet = function (seed, options) {
         return tx
     }
 
+    function checkDust(value){
+      if (isNullOrUndefined(value) || value < 5430) {
+        throw new Error("Value below dust threshold")
+      }
+    }
+
     function estimateFeePadChangeOutput(tx){
         var tmpTx = tx.clone()
         tmpTx.addOutput(getChangeAddress(), 0)

test/wallet.js

@@ -367,10 +367,6 @@ describe('Wallet', function() {
       }
     })
 
-    function fakeTxHash(i) {
-      return "txtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtx" + i
-    }
-
     describe('choosing utxo', function(){
       it('calculates fees', function(){
         var tx = wallet.createTx(to, value)
@@ -441,6 +437,20 @@ describe('Wallet', function() {
         assert(Transaction.prototype.sign.calledWith(1, wallet.getPrivateKeyForAddress(address1)))
       })
     })
+
+    describe('when value is below dust threshold', function(){
+      it('throws an error', function(){
+        var value = 5429
+
+        assert.throws(function() {
+          wallet.createTx(to, value)
+        }, Error, 'Value below dust threshold')
+      })
+    })
+
+    function fakeTxHash(i) {
+      return "txtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtxtx" + i
+    }
   })
 
   function assertEqual(obj1, obj2){