diff --git a/js/utils.js b/js/utils.js
new file mode 100644
index 0000000..79e132d
--- /dev/null
+++ b/js/utils.js
@@ -0,0 +1,10 @@
+function validateExtension(file) {
+  const fileName = file.name;
+  const fileExtension =fileName.substr(fileName.lastIndexOf('.')).toLowerCase();
+
+  const _validFileExtensions = [".jpg", ".jpeg", ".bmp", ".gif", ".png"];
+
+  return _validFileExtensions.find((ext) => fileExtension === ext) || null;
+}
+
+module.exports = {validateExtension};
\ No newline at end of file
diff --git a/package.json b/package.json
index 3658c84..b3fc019 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,7 @@
   "description": "HTML5 inApp support chat using your own firebase account",
   "main": "index.js",
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "./node_modules/mocha/bin/mocha"
   },
   "repository": {
     "type": "git",
@@ -34,6 +34,7 @@
   "homepage": "https://github.com/CodingCarlos/inapp-support#readme",
   "devDependencies": {
     "browser-sync": "^2.18.2",
+    "chai": "^3.5.0",
     "gulp": "^3.9.1",
     "gulp-clean": "^0.3.2",
     "gulp-concat": "^2.6.1",
@@ -42,6 +43,7 @@
     "gulp-rename": "^1.2.2",
     "gulp-sourcemaps": "^1.9.1",
     "gulp-uglify": "^2.0.0",
+    "mocha": "^3.2.0",
     "run-sequence": "^1.2.2"
   }
 }
diff --git a/test/chat.js b/test/chat.js
new file mode 100644
index 0000000..1857c08
--- /dev/null
+++ b/test/chat.js
@@ -0,0 +1,56 @@
+const expect = require('chai').expect;
+
+const utils = require('../js/utils');
+
+describe('Chat inapp', () => {
+  describe('validates file extensions', () => {
+    it('jpg is a valid extension', () => {
+      const file = {name:'chat.jpg'};
+
+      const ext = utils.validateExtension(file);
+      
+      expect(ext).to.equal('.jpg');
+    });
+
+    it('png is a valid extension', () => {
+      const file = {name:'chat.png'};
+
+      const ext = utils.validateExtension(file);
+
+      expect(ext).to.equal('.png');
+    });
+    
+    it('js is NOT a valid extension', () => {
+      const file = {name:'chat.js'};
+      
+      const ext = utils.validateExtension(file);
+      
+      expect(ext).to.be.null;
+    });
+    
+    it('PNG is a valid extension', () => {
+      const file = {name:'chat.PNG'};
+      
+      const ext = utils.validateExtension(file);
+      
+      expect(ext).to.equal('.png');
+    });
+    
+    it('no extension is NOT valid', () => {
+      const file = {name:'chat'};
+      
+      const ext = utils.validateExtension(file);
+
+      expect(ext).to.be.null;
+    });
+
+    it('just extension is NOT valid', () => {
+      const file = {name:'jpg'};
+      
+      const ext = utils.validateExtension(file);
+
+      expect(ext).to.be.null;
+    });
+
+  });
+});
\ No newline at end of file