diff --git a/.travis.yml b/.travis.yml
index 76fd222..7bec32f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,6 +11,7 @@ node_js:
 before_install:
   - "npm install -g mocha"
   - "npm install chai"
+  - "npm install selenium-webdriver"
 
 notifications:
   email: false
diff --git a/calculator.js b/calculator.js
index caf34db..cc8e71f 100644
--- a/calculator.js
+++ b/calculator.js
@@ -1,5 +1,5 @@
 function isNumber(numStr){
-  var re = /^[0-9\.]+$/; 
+  var re=/^[+-]?[0-9]+\.{0,1}[0-9]*$/
   return re.test(numStr);
 }
 
@@ -10,6 +10,14 @@ function add(num1, num2){
 function substract(num1, num2){
   return num1 - num2;
 }
-
+function mul(num1,num2){
+    return num1*num2;
+}
+function div(num1,num2){
+    return num1/num2;
+}
+module.exports.substract=substract;
+module.exports.div=div;
+module.exports.mul=mul;
 module.exports.add = add;
 module.exports.isNumber = isNumber;
diff --git a/index.html b/index.html
index cc6a9d9..5bcf6a3 100644
--- a/index.html
+++ b/index.html
@@ -20,8 +20,10 @@
     <h1>Silly Calculator</h1>
     <input type="text" name="" id="num1" value="1" />
     <select id="operator" size="1">
-      <option value="add">+</option>
-      <option value="substract">-</option>
+      <option value="add">＋</option>
+      <option value="substract">－</option>
+      <option value="mul">×</option>
+      <option value="div">÷</option>
     </select>
     <input type="text" id="num2" value="1" />
     <div>=</div>
diff --git a/main.js b/main.js
index 957a234..7523089 100644
--- a/main.js
+++ b/main.js
@@ -1,23 +1,34 @@
 window.onload = function(){
-  document.getElementById('go_btn').onclick = function(){
-    var num1Str = document.getElementById('num1').value;
-    var num2Str = document.getElementById('num2').value;
-    if (!isNumber(num1Str) || !isNumber(num2Str)){
-      alert("Some of the input is not a number!")
-      document.getElementById('ans').value = "ERROR"
-      return
+    document.getElementById('go_btn').onclick = function(){
+        var num1Str = document.getElementById('num1').value;
+        var num2Str = document.getElementById('num2').value;
+        if (!isNumber(num1Str) || !isNumber(num2Str)){
+            alert("Some of the input is not a number!")
+            document.getElementById('ans').value = "ERROR"
+            return
+        }
+        var num1 = parseFloat(num1Str)
+        var num2 = parseFloat(num2Str)
+        var operator = document.getElementById('operator').value;
+        if (operator == "add"){
+            document.getElementById('ans').value = add(num1, num2);
+        }
+        else if (operator == "substract"){
+            document.getElementById('ans').value = substract(num1, num2);
+        }
+        else if (operator == "mul"){
+            document.getElementById('ans').value = mul(num1,num2);
+        }
+        else if (operator == "div"){
+            if(num2===0){
+                document.getElementById('ans').value = "ERROR"
+            }
+            else{
+                document.getElementById('ans').value = div(num1,num2);
+            }
+        }
+        else {
+            alert("Bad operator!")
+        }
     }
-    var num1 = parseFloat(num1Str)
-    var num2 = parseFloat(num2Str)
-    var operator = document.getElementById('operator').value;
-    if (operator == "add"){
-      document.getElementById('ans').value = add(num1, num2);
-    }
-    else if (operator == "substract"){
-      document.getElementById('ans').value = substract(num1, num2);
-    }
-    else {
-      alert("Bad operator!")
-    }
-  }
 }
diff --git a/package.json b/package.json
index d727f6d..b77db86 100644
--- a/package.json
+++ b/package.json
@@ -8,7 +8,9 @@
   "author": "Askeing Yen & Shing Lyu",
   "license": "MPLv2",
   "dependencies": {
-    "mocha": "~2.3.2"
+    "mocha": "~2.3.2",
+    "sinon": "~1.17.2"
   },
   "repository":{}
+  
 }
diff --git a/selenium_test.js b/selenium_test.js
new file mode 100644
index 0000000..c00ec4c
--- /dev/null
+++ b/selenium_test.js
@@ -0,0 +1,17 @@
+var webdriver = require('selenium-webdriver');
+var assert = require('assert');
+
+var driver = new webdriver.Builder().
+    forBrowser('chrome').build();
+    driver.get("http://127.0.0.1:8000/")
+    var searchBox=driver.findElement(webdriver.By.id('num1'));
+    searchBox.sendKeys('1');
+    var searchBox2=driver.findElement(webdriver.By.id('num2'));
+    searchBox2.sendKeys('1');
+    driver.findElement(webdriver.By.id('go_btn')).click();
+    var searchBoxResult = driver.findElement(webdriver.By.id('ans'));
+    searchBoxResult.getAttribute('value').then(function(value){
+        console.log(value);
+        assert.equal(value,'22');
+    });
+
diff --git a/test/test_calculator.js b/test/test_calculator.js
index 13f6205..3d7a5a8 100644
--- a/test/test_calculator.js
+++ b/test/test_calculator.js
@@ -1,10 +1,95 @@
 var assert = require('assert');
 var cal = require('../calculator.js')
+var sinon=require('sinon')
+
+//var webdriver = require('selenium-webdriver');
+//webdriver = require('selenium-webdriver');
+//var driver =undefined;
 
 describe('Calculator', function(){
-  describe('add', function(){
-    it('add', function(){
-      assert.equal('2', cal.add(1, 1));
+    describe('add', function(){
+        it('add', function(){
+            assert.equal('2', cal.add(1, 1));
+        })
+        it('add_decimal', function(){
+            assert.equal('2.2', cal.add(1.1, 1.1));
+        })
+        it('add_neg', function(){
+            assert.equal('-2', cal.add(-1,-1));
+        })
+        it('add_neg', function(){
+            assert.equal('-2', cal.add(-1,-1));
+        })
+
+    })
+    describe('sub', function(){
+        it('sub', function(){
+            assert.equal('0', cal.substract(1, 1));
+        })
+        it('sub_decimal',function(){
+            assert.equal('0',cal.substract(1.1,1.1));
+        })
+        it('sub_neg',function(){
+            assert.equal('0',cal.substract(-13.15,-13.15));
+        })
+    })
+    describe('mul', function(){
+        it('mul', function(){
+            assert.equal('1', cal.mul(1, 1));
+        })
+
+        it('mul_decimal', function(){
+            assert.equal('65', cal.mul(0.65,100));
+        })
+        it('mul_neg', function(){
+            assert.equal('-11', cal.mul(-11, 1));
+        })
+    })
+    describe('div', function(){
+        it('div', function(){
+            assert.equal('1', cal.div(1, 1));
+        })
+        it('div_decimal', function(){
+            assert.equal('1', cal.div(1.1, 1.1));
+        })
+        it('div_neg', function(){
+            assert.equal('-1', cal.div(-1, 1));
+        })
+    })
+
+    describe('negative_test', function(){
+        it('shold be false', function(){
+            assert.equal(false, cal.isNumber('a'));
+            assert.equal(true, cal.isNumber(1));
+        })
+    })
+    describe('sinon_test',function(){
+        it('Sinon test',function(){
+            var stub = sinon.stub(Math,"random").returns(39);
+
+            assert.equal(39,cal.mul(Math.random(),1));
+        })
     })
-  })
+
+
+   /* describe('selenium-webdriver',function(){
+        it('selenium-test',function(done){
+            var driver = new webdriver.Builder().
+                forBrowser('chrome').build();
+                driver.get("http://127.0.0.1:8000/")
+                var searchBox=driver.findElement(webdriver.By.id('num1'));
+                searchBox.sendKeys('1');
+                var searchBox2=driver.findElement(webdriver.By.id('num2'));
+                searchBox2.sendKeys('1');
+                driver.findElement(webdriver.By.id('go_btn')).click();
+                var searchBoxResult = driver.findElement(webdriver.By.id('ans'));
+                searchBoxResult.getAttribute('value').then(function(value){
+                    console.log(value);
+                    assert.equal(value,'3');
+                });
+                //driver.quit();    
+        })
+    })*/
+
+
 })