Added serialize method for transaction

Author: rg911

src/model/transaction/Transaction.ts

@@ -15,6 +15,7 @@
  */
 
 import { VerifiableTransaction } from 'nem2-library';
+import { SerializeTransactionToJSON } from '../../infrastructure/transaction/SerializeTransactionToJSON';
 import { Account } from '../account/Account';
 import { PublicAccount } from '../account/PublicAccount';
 import { NetworkType } from '../blockchain/NetworkType';
@@ -25,7 +26,6 @@ import { InnerTransaction } from './InnerTransaction';
 import { SignedTransaction } from './SignedTransaction';
 import { TransactionInfo } from './TransactionInfo';
 import { TransactionType } from './TransactionType';
-import { SerializeTransactionToJSON } from '../../infrastructure/transaction/SerializeTransactionToJSON';
 
 /**
  * An abstract transaction class that serves as the base class of all NEM transactions.
@@ -176,7 +176,19 @@ export abstract class Transaction {
     }
 
     /**
-     * Create JSON object
+     * @description Serialize a transaction object
+     * @returns {string}
+     * @memberof Transaction
+     */
+    public serialize() {
+        const transaction = this.buildTransaction();
+        return transaction.serializeUnsignedTransaction();
+    }
+
+    /**
+     * @description Create JSON object
+     * @returns {Object}
+     * @memberof Transaction
      */
     public toJSON() {
         const commonTransactionObject = {

src/utility/TransactionMapping.ts

@@ -37,20 +37,4 @@ export class TransactionMapping {
     public static createFromPayload(dataBytes: string): Transaction {
         return CreateTransactionFromPayload(dataBytes);
     }
-
-    /**
-     * Serialize a transaction.
-     * @returns {string} Serialized transaction in binary.
-     */
-    public static serialize(): string {
-        throw new Error();
-    }
-
-    /**
-     * Create transaction class from Json.
-     * @returns {object} Serialized transaction in json object.
-     */
-    public static serializeJson(): object {
-        throw new Error();
-    }
 }

test/model/transaction/Transaction.spec.ts

@@ -180,6 +180,24 @@ describe('Transaction', () => {
             }).to.throw(Error, 'Inner transaction cannot be an aggregated transaction.');
         });
     });
+    
+    describe('Transaction serialize', () => {
+        it('Should return serialized payload', () => {
+            const transaction = TransferTransaction.create(
+                Deadline.create(),
+                Address.createFromRawAddress('SBILTA367K2LX2FEXG5TFWAS7GEFYAGY7QLFBYKC'),
+                [],
+                PlainMessage.create('test-message'),
+                NetworkType.MIJIN_TEST,
+            );
+            const serialized = transaction.serialize();
+
+            expect(serialized.substring(
+                240,
+                serialized.length,
+            )).to.be.equal('9050B9837EFAB4BBE8A4B9BB32D812F9885C00D8FC1650E1420D000000746573742D6D657373616765');
+        });
+    });
 });
 
 class FakeTransaction extends Transaction {