[FABN-838] update BlockDecoder.timeStampToDate()

BlockDecoder.timeStampToDate() use Date.toString() which lose the date
precision of nanoseconds.

FABN-838 #done

Change-Id: I4435bfd2bca8bcc5f5a160d654f9a26cd92c52ce
Signed-off-by: zhaochy <[email protected]>

fabric-client/lib/BlockDecoder.js

@@ -1086,7 +1086,7 @@ function timeStampToDate(time_stamp) {
 	const millis = time_stamp.seconds * 1000 + time_stamp.nanos / 1000000;
 	const date = new Date(millis);
 
-	return date.toString();
+	return date.toISOString();
 }
 
 function decodeChaincodeActionPayload(payload_bytes) {

fabric-client/test/BlockDecoder.js

@@ -0,0 +1,31 @@
+/*
+ Copyright 2018 IBM All Rights Reserved.
+
+ SPDX-License-Identifier: Apache-2.0
+
+*/
+
+const rewire = require('rewire');
+const BlockDecoderRewire = rewire('../lib/BlockDecoder');
+require('chai').should();
+
+describe('BlockDecoder', () => {
+	describe('timeStampToDate()', () => {
+		const timeStampToDate = BlockDecoderRewire.__get__('timeStampToDate');
+
+		it('should return null for empty timestamp', () => {
+			const res = timeStampToDate();
+			res.should.eql('null');
+		});
+
+		it('should return ISO8601 string for a valid timestamp', () => {
+			const now = new Date();
+			const timestamp = {
+				seconds: Math.floor(now.getTime()/1000),
+				nanos: now.getMilliseconds() * 1000000
+			};
+			const res = timeStampToDate(timestamp);
+			res.should.have.string(now.getMilliseconds().toString());
+		});
+	});
+});