more test case

test/response/header.js

@@ -7,4 +7,12 @@ describe('res.header', function(){
     res.set('X-Foo', 'bar');
     res.header.should.eql({ 'x-foo': 'bar' });
   })
+
+  describe('when res._headers not present', function (){
+    it('should return empty object', function (){
+      var res = response();
+      res.res._headers = null;
+      res.header.should.eql({});
+    })
+  })
 })

test/response/last-modified.js

@@ -24,4 +24,11 @@ describe('res.lastModified', function(){
     (res.lastModified.getTime() / 1000)
     .should.equal(Math.floor(date.getTime() / 1000));
   })
+
+  describe('when lastModified not set', function (){
+    it('should get undefined', function(){
+      var res = response();
+      (res.lastModified === undefined).should.be.ok;
+    })
+  })
 })

test/response/writeable.js

@@ -0,0 +1,17 @@
+
+var response = require('../context').response;
+
+describe('res.writable', function(){
+  it('should return the request is writable', function(){
+    var res = response();
+    res.writable.should.be.ok;
+  })
+
+  describe('when res.socket not present', function (){
+    it('should return the request is not writable', function (){
+      var res = response();
+      res.res.socket = null;
+      res.writable.should.not.be.ok;
+    })
+  })
+})