diff --git a/lib/specs/spec_0_2.js b/lib/specs/spec_0_2.js
index 94ca6bb..210f600 100644
--- a/lib/specs/spec_0_2.js
+++ b/lib/specs/spec_0_2.js
@@ -1,4 +1,5 @@
-var uuid = require('uuid/v4');
+var uuid  = require('uuid/v4');
+var empty = require('is-empty')
 
 function Spec_0_2(){
   this.payload = {
@@ -12,6 +13,22 @@ function Spec_0_2(){
  */
 Spec_0_2.prototype.check = function(){
 
+  if(empty(this.payload['type'])) {
+    throw {message: "'type' is invalid"};
+  }
+
+  if(empty(this.payload['specversion'])) {
+    throw {message: "'specversion' is invalid"};
+  }
+
+  if(this.payload['specversion'] !== '0.2') {
+    throw {message: "'specversion' value is invalid: '" 
+      + this.payload['specversion'] + "'"};
+  }
+
+  if(empty(this.payload['id'])) {
+    throw {message: "'id' is invalid"};
+  }
 }
 
 Spec_0_2.prototype.type = function(_type){
@@ -34,7 +51,25 @@ Spec_0_2.prototype.time = function(_time){
   return this;
 }
 
-//TODO another attributes . . .
+Spec_0_2.prototype.schemaurl = function(_schemaurl){
+  this.payload['schemaurl'] = _schemaurl;
+  return this;
+}
+
+Spec_0_2.prototype.contenttype = function(_contenttype){
+  this.payload['contenttype'] = _contenttype;
+  return this;
+}
+
+Spec_0_2.prototype.data = function(_data){
+  this.payload['data'] = _data;
+  return this;
+}
+
+Spec_0_2.prototype.addExtension = function(key, value){
+  this.payload[key] = value;
+  return this;
+}
 
 module.exports = Spec_0_2;
 
diff --git a/test/cloudevent_spec_0_2.js b/test/cloudevent_spec_0_2.js
index a94faa1..18c71f1 100644
--- a/test/cloudevent_spec_0_2.js
+++ b/test/cloudevent_spec_0_2.js
@@ -1,9 +1,17 @@
 var expect     = require("chai").expect;
 var Cloudevent = require("../index.js");
 
+const type   = "com.github.pull.create";
+const source = "urn:event:from:myapi/resourse/123";
+const time   = new Date();
+const schemaurl = "http://example.com/registry/myschema.json";
+const contenttype = "application/json";
+const data = {};
+const extensions = {};
+
 var cloudevent = new Cloudevent(Cloudevent.specs['0.2'])
-                       .type("com.github.pull.create")
-                       .source("urn:event:from:myapi/resourse/123");
+                       .type(type)
+                       .source(source);
 
 describe("CloudEvents Spec 0.2 - JavaScript SDK", () => {
 
@@ -27,6 +35,91 @@ describe("CloudEvents Spec 0.2 - JavaScript SDK", () => {
       });
     });
 
+    describe("Optional context attributes", () => {
+      it("contains 'time'", () => {
+        cloudevent.time(time);
+        expect(cloudevent.format()).to.have.property('time');
+      });
+
+      it("contains 'schemaurl'", () => {
+        cloudevent.schemaurl(schemaurl);
+        expect(cloudevent.format()).to.have.property('schemaurl');
+      });
+
+      it("contains 'contenttype'", () => {
+        cloudevent.contenttype(contenttype);
+        expect(cloudevent.format()).to.have.property('contenttype');
+      });
+
+      it("contains 'data'", () => {
+        cloudevent.data(data);
+        expect(cloudevent.format()).to.have.property('data');
+      });
+
+      it("contains 'extension1'", () => {
+        cloudevent.addExtension("extension1", "value1");
+        expect(cloudevent.format()).to.have.property('extension1');
+      });
+
+      it("'extension2' should have value equals to 'value1'", () => {
+        cloudevent.addExtension("extension2", "value2");
+        expect(cloudevent.format()['extension2']).to.equal('value2');
+      });
+    });
+
+    describe("The Constraints check", () => {
+      describe("'type'", () => {
+        it("should throw an error when is an empty string", () => {
+          cloudevent.type("");
+          expect(cloudevent.format.bind(cloudevent))
+            .to
+            .throw("'type' is invalid");
+        });
+
+        it("must be a non-empty string", () => {
+          cloudevent.type(type);
+          cloudevent.format();
+        });
+
+        it("should be prefixed with a reverse-DNS name", () => {
+          //TODO how to assert it?
+        });
+      });
+
+      describe("'specversion'", () => {
+        it("compliant event producers must use a value of '0.2'", () => {
+          expect(cloudevent.format()['specversion']).to.equal("0.2");
+        });
+
+        it("should throw an error when is an empty string", () => {
+          cloudevent.spec.payload.specversion = "";
+          expect(cloudevent.format.bind(cloudevent))
+            .to
+            .throw("'specversion' is invalid");
+          cloudevent.spec.payload.specversion = "0.2";
+        });
+      });
+
+      describe("'id'", () => {
+        it("should throw an error when is an empty string", () => {
+          cloudevent.id("");
+          expect(cloudevent.format.bind(cloudevent))
+            .to
+            .throw("'id' is invalid");
+        });
+        it("must be a non-empty string", () => {
+          cloudevent.id("my.id-0x0090");
+          cloudevent.format();
+        });
+      });
+
+      describe("'time'", () => {
+        it("must adhere to the format specified in RFC 3339", () => {
+          cloudevent.time(time);
+          expect(cloudevent.format()['time']).to.equal(time.toISOString());
+        });
+      });
+    });
   });
 
 });