Added test cases to check for res._header and res.headersSent equ…

…ivalence

test/session.js

@@ -1381,6 +1381,29 @@ describe('session()', function(){
     })
   });
 
+  describe('res._header patch', function () {
+    it('should be equivalent to res.headersSent', function (done) {
+      request(createServer(function(req, res) {
+        var priorHeader = !!res._header
+        var priorHeadersSent = !!res.headersSent
+        assert.strictEqual(priorHeader, priorHeadersSent,
+          'res._header should be equal to res.headersSent (prior state change')
+
+        res.end('ended')
+
+        var afterHeader = !!res._header
+        var afterHeadersSent = !!res.headersSent
+        assert.strictEqual(afterHeader, afterHeadersSent,
+          'res._header should be equal to res.headersSent (after state change)')
+
+        assert.notStrictEqual(priorHeader, afterHeader)
+        assert.notStrictEqual(priorHeadersSent, afterHeadersSent)
+      }))
+      .get('/')
+      .expect(200, 'ended', done)
+    })
+  })
+
   describe('res.end patch', function () {
     it('should correctly handle res.end/res.write patched prior', function (done) {
       function setup (req, res) {