diff --git a/src/Validators/TransactionValidator.php b/src/Validators/TransactionValidator.php
index 4fd7b67..ccb3994 100644
--- a/src/Validators/TransactionValidator.php
+++ b/src/Validators/TransactionValidator.php
@@ -20,7 +20,9 @@ class TransactionValidator
 {
     /**
      * validate
-     *
+     * To do: check is data optional?
+     * Data is not optional on spec, see https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sendtransaction
+     * 
      * @param array $value
      * @return bool
      */
@@ -35,7 +37,7 @@ class TransactionValidator
         if (AddressValidator::validate($value['from']) === false) {
             return false;
         }
-        if (isset($value['to']) && AddressValidator::validate($value['to']) === false && $value['to'] !== '') {
+        if (isset($value['to']) && AddressValidator::validate($value['to']) === false) {
             return false;
         }
         if (isset($value['gas']) && QuantityValidator::validate($value['gas']) === false) {
@@ -47,9 +49,15 @@ class TransactionValidator
         if (isset($value['value']) && QuantityValidator::validate($value['value']) === false) {
             return false;
         }
-        if (isset($value['data']) && HexValidator::validate($value['data']) === false) {
+        if (!isset($value['data'])) {
             return false;
         }
+        if (HexValidator::validate($value['data']) === false) {
+            return false;
+        }
+        // if (isset($value['data']) && HexValidator::validate($value['data']) === false) {
+        //     return false;
+        // }
         if (isset($value['nonce']) && QuantityValidator::validate($value['nonce']) === false) {
             return false;
         }
diff --git a/test/unit/TransactionValidatorTest.php b/test/unit/TransactionValidatorTest.php
new file mode 100644
index 0000000..ce12915
--- /dev/null
+++ b/test/unit/TransactionValidatorTest.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace Test\Unit;
+
+use Test\TestCase;
+use Web3\Validators\TransactionValidator;
+
+class TransactionValidatorTest extends TestCase
+{
+    /**
+     * validator
+     * 
+     * @var \Web3\Validators\TransactionValidator
+     */
+    protected $validator;
+
+    /**
+     * setUp
+     * 
+     * @return void
+     */
+    public function setUp()
+    {
+        parent::setUp();
+        $this->validator = new TransactionValidator;
+    }
+
+    /**
+     * testValidate
+     * 
+     * @return void
+     */
+    public function testValidate()
+    {
+        $validator = $this->validator;
+
+        $this->assertEquals(false, $validator->validate('hello web3.php'));
+        $this->assertEquals(false, $validator->validate([]));
+        $this->assertEquals(false, $validator->validate([
+            'from' => '',
+        ]));
+        $this->assertEquals(false, $validator->validate([
+            'from' => '0xb60e8dd61c5d32be8058bb8eb970870f07233155',
+            'data' => ''
+        ]));
+        $this->assertEquals(true, $validator->validate([
+            'from' => '0xb60e8dd61c5d32be8058bb8eb970870f07233155',
+            'data' => '0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675'
+        ]));
+        $this->assertEquals(true, $validator->validate([
+            'from' => '0xb60e8dd61c5d32be8058bb8eb970870f07233155',
+            'to' => '0xd46e8dd67c5d32be8058bb8eb970870f07244567',
+            'gas' => '0x76c0',
+            'gasPrice' => '0x9184e72a000',
+            'value' => '0x9184e72a',
+            'data' => '0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675'
+        ]));
+    }
+}
\ No newline at end of file