Add error tests

Author: Ruben Bridgewater

package.json

@@ -6,7 +6,8 @@
   "scripts": {
     "test": "npm run coverage",
     "benchmark": "node ./benchmark",
-    "posttest": "standard && npm run coverage:check",
+    "lint": "standard --fix",
+    "posttest": "npm run lint && npm run coverage:check",
     "coverage": "node ./node_modules/istanbul/lib/cli.js cover --preserve-comments ./node_modules/mocha/bin/_mocha -- -R spec",
     "coverage:check": "node ./node_modules/istanbul/lib/cli.js check-coverage --branch 100 --statement 100"
   },

test/errors.spec.js

@@ -0,0 +1,22 @@
+'use strict'
+
+/* eslint-env mocha */
+
+var assert = require('assert')
+var ReplyError = require('../lib/replyError')
+var ParserError = require('../lib/parserError')
+var RedisError = require('../lib/redisError')
+
+describe('errors', function () {
+  it('errors should have a stack trace with error message', function () {
+    var err1 = new RedisError('test')
+    var err2 = new ReplyError('test')
+    var err3 = new ParserError('test', new Buffer(''), 0)
+    assert(err1.stack)
+    assert(err2.stack)
+    assert(err3.stack)
+    assert(/RedisError: test/.test(err1.stack))
+    assert(/ReplyError: test/.test(err2.stack))
+    assert(/ParserError: test/.test(err3.stack))
+  })
+})