diff --git a/app/models/user.js b/app/models/user.js
index ca122265e1..d726835960 100755
--- a/app/models/user.js
+++ b/app/models/user.js
@@ -15,7 +15,7 @@ var mongoose = require('mongoose'),
 var UserSchema = new Schema({
     name: String,
     email: String,
-    username: String,
+    username: {type: String, unique: true},
     provider: String,
     hashed_password: String,
     facebook: {},
diff --git a/test/article/model.js b/test/article/model.js
index e31351abae..86b8d1d1a3 100644
--- a/test/article/model.js
+++ b/test/article/model.js
@@ -52,7 +52,14 @@ describe('<Unit Test>', function() {
         });
 
         afterEach(function(done) {
+            Article.remove({});
+            User.remove({});
+            done();
+        });
+        after(function(done){
+            Article.remove().exec();
+            User.remove().exec();
             done();
         });
     });
-});
\ No newline at end of file
+});
diff --git a/test/user/model.js b/test/user/model.js
index 4919b7b543..d72c14eb48 100644
--- a/test/user/model.js
+++ b/test/user/model.js
@@ -19,15 +19,33 @@ describe('<Unit Test>', function() {
                 username: 'user',
                 password: 'password'
             });
+            user2 = new User({
+                name: 'Full name',
+                email: 'test@test.com',
+                username: 'user',
+                password: 'password'
+            });
 
             done();
         });
 
         describe('Method Save', function() {
+            it('should begin with no users', function(done){
+                User.find({}, function(err,users){
+                  users.should.have.length(0);
+                  done();
+                });
+            });
+
             it('should be able to save whithout problems', function(done) {
-                return user.save(function(err) {
-                    should.not.exist(err);
-                    done();
+                user.save(done);
+            });
+
+            it('should fail to save an existing user again', function(done) {
+                user.save();
+                return user2.save(function(err){
+                  should.exist(err);
+                  done();
                 });
             });
 
@@ -41,7 +59,8 @@ describe('<Unit Test>', function() {
         });
 
         after(function(done) {
+            User.remove().exec();
             done();
         });
     });
-});
\ No newline at end of file
+});