diff --git a/.jshintrc b/.jshintrc
index 604e4aac04c1fa97affb0778328c62f722d5feb2..ef71670d231fb7785aadb929c05be8ce97641a7f 100644
--- a/.jshintrc
+++ b/.jshintrc
@@ -17,5 +17,8 @@
   "esnext": true,
   "eqnull": true,
   "browser": true,
-  "worker": true
+  "worker": true,
+  "globals": {
+    "JSON": false
+  }
 }
diff --git a/package.json b/package.json
index a8e396d231e8efb8a2daf4d7463c573646d8cc4c..d3dd61ae59f95fd2280500391ec3b29c1922454f 100644
--- a/package.json
+++ b/package.json
@@ -13,10 +13,10 @@
   "devDependencies": {
     "bower": "1.3.8",
     "chai": "1.10.0",
-    "jshint": "2.5.2",
+    "jshint": "2.8.0",
     "mocha-phantomjs": "3.5.2",
     "mocha": "2.1.0",
-    "phantomjs": "1.9.13"
+    "phantomjs": "1.9.19"
   },
   "files" : [
     "LICENSE",
diff --git a/script/phantomjs b/script/phantomjs
index 2689f41ad5002f1e2a44dee186508214b39d0a57..757e7ea3d9aa8f3ef6feb726941a580c07eeb8f8 100755
--- a/script/phantomjs
+++ b/script/phantomjs
@@ -12,5 +12,16 @@ node ./script/server $port &>/dev/null &
 server_pid=$!
 trap "kill $server_pid" INT EXIT
 
-node ./node_modules/.bin/mocha-phantomjs -s localToRemoteUrlAccessEnabled=true -s webSecurityEnabled=false "http://localhost:$port/test/test.html"
-node ./node_modules/.bin/mocha-phantomjs -s localToRemoteUrlAccessEnabled=true -s webSecurityEnabled=false "http://localhost:$port/test/test-worker.html"
+STATUS=0
+
+run() {
+  node ./node_modules/.bin/mocha-phantomjs \
+    -s localToRemoteUrlAccessEnabled=true \
+    -s webSecurityEnabled=false \
+    "$@" || STATUS=$?
+}
+
+run "http://localhost:$port/"
+run "http://localhost:$port/test/test-worker.html"
+
+exit $STATUS
diff --git a/script/saucelabs b/script/saucelabs
index 98d9a937677cebc54b4ca0bfbf94d19349121cb7..a47e36a51666b446a1eb7e0bdb7696f19209f742 100755
--- a/script/saucelabs
+++ b/script/saucelabs
@@ -25,7 +25,7 @@ job="$(./script/saucelabs-api --raw "js-tests" <<JSON
     "tags": ["$TRAVIS_PULL_REQUEST", "$TRAVIS_BRANCH"],
     "tunnel-identifier": "$TRAVIS_JOB_NUMBER",
     "platforms": [["$SAUCE_PLATFORM", "$SAUCE_BROWSER", "$SAUCE_VERSION"]],
-    "url": "http://localhost:$port/test/test.html",
+    "url": "http://localhost:$port/",
     "framework": "mocha"
   }
 JSON
diff --git a/script/server b/script/server
index b41c6b85a0e07aa48da0e26c4ef28e5b5755a826..00993f84f0cc63d86e63441c555c2c640e7be9e5 100755
--- a/script/server
+++ b/script/server
@@ -123,12 +123,13 @@ var types = {
   txt: 'text/plain'
 };
 
-http.createServer(function(req, res) {
+server = http.createServer(function(req, res) {
   var pathname = url.parse(req.url).pathname;
   var route = routes[pathname];
   if (route) {
     route(res, req);
   } else {
+    if (pathname == '/') pathname = '/test/test.html'
     fs.readFile(__dirname + '/..' + pathname, function(err, data) {
       if (err) {
         res.writeHead(404, {'Content-Type': types.txt});
@@ -140,4 +141,8 @@ http.createServer(function(req, res) {
       }
     });
   }
-}).listen(port);
+});
+
+console.warn("Started test server on localhost:" + port);
+server.listen(port);
+
diff --git a/test/.jshintrc b/test/.jshintrc
index 2fa08ad76783c5349f3c19bcf1c115ea29ec2adb..300079e46d4e0654ca883348af5ba24ba7b7cc60 100644
--- a/test/.jshintrc
+++ b/test/.jshintrc
@@ -1,22 +1,8 @@
 {
-  "curly": true,
-  "eqeqeq": true,
-  "immed": true,
-  "indent": 2,
-  "latedef": true,
-  "newcap": true,
-  "noarg": true,
-  "quotmark": true,
-  "undef": true,
-  "unused": true,
-  "trailing": true,
-  "asi": true,
-  "boss": true,
-  "esnext": true,
+  "extends": "../.jshintrc",
+  "es3": false,
+  "strict": false,
   "sub": true,
-  "eqnull": true,
-  "browser": true,
-  "worker": true,
   "globals": {
     "fetch": false,
     "Headers": false,
@@ -26,6 +12,7 @@
     "chai": false,
     "suite": false,
     "setup": false,
+    "suiteSetup": false,
     "test": false,
     "assert": false
   }
diff --git a/test/test-worker.html b/test/test-worker.html
index 6ff9dd5231c6834f55b361ce7976b364fa6928ed..57f4a51c6502a177a9587a31d594717b354bd858 100644
--- a/test/test-worker.html
+++ b/test/test-worker.html
@@ -3,16 +3,16 @@
 <head>
   <meta charset="utf-8">
   <title>Fetch Worker Tests</title>
-  <link rel="stylesheet" href="../node_modules/mocha/mocha.css" />
+  <link rel="stylesheet" href="/node_modules/mocha/mocha.css" />
 </head>
 <body>
   <div id="mocha"></div>
-  <script src="../node_modules/mocha/mocha.js"></script>
+  <script src="/node_modules/mocha/mocha.js"></script>
 
   <script>
     mocha.setup('tdd')
 
-    var worker = new Worker('worker.js')
+    var worker = new Worker('/test/worker.js')
 
     worker.addEventListener('message', function(e) {
       switch (e.data.name) {
diff --git a/test/test.html b/test/test.html
index 8047ec51ab3ae33f47086598a8d0e7a9a4d9f315..0d51696bcff955677d7934dc052200d3c52876de 100644
--- a/test/test.html
+++ b/test/test.html
@@ -3,21 +3,24 @@
 <head>
   <meta charset="utf-8">
   <title>Fetch Tests</title>
-  <link rel="stylesheet" href="../node_modules/mocha/mocha.css" />
+  <link rel="stylesheet" href="/node_modules/mocha/mocha.css" />
 </head>
 <body>
   <div id="mocha"></div>
-  <script src="../node_modules/chai/chai.js"></script>
-  <script src="../node_modules/mocha/mocha.js"></script>
+  <script src="/node_modules/chai/chai.js"></script>
+  <script src="/node_modules/mocha/mocha.js"></script>
   <script>
-    mocha.setup('tdd')
-    self.assert = chai.assert
+    if (self.mocha && mocha.setup) {
+      mocha.setup('tdd')
+      self.assert = chai.assert
+    } else {
+      document.write('<p>Error: please run <code>make</code> to install dependencies and try again.</p>')
+    }
   </script>
 
-  <script src="../bower_components/es6-promise/promise.js"></script>
-  <script src="../fetch.js"></script>
-
-  <script src="test.js"></script>
+  <script src="/bower_components/es6-promise/promise.js"></script>
+  <script src="/test/test.js"></script>
+  <script src="/fetch.js"></script>
 
   <script>
     if (self.mochaPhantomJS) {
diff --git a/test/test.js b/test/test.js
index 5cdd6751e08b7d6674fee041f0123e24344da9c7..6c31b610eb620fba2e93bef49eefefba2110153c 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1,3 +1,18 @@
+var support = {
+  blob: 'FileReader' in self && 'Blob' in self && (function() {
+    try {
+      new Blob()
+      return true
+    } catch(e) {
+      return false
+    }
+  })(),
+  formData: 'FormData' in self,
+  arrayBuffer: 'ArrayBuffer' in self,
+  patch: !/PhantomJS/.test(navigator.userAgent),
+  permanentRedirect: !/PhantomJS|Trident/.test(navigator.userAgent)
+}
+
 function readBlobAsText(blob) {
   if ('FileReader' in self) {
     return new Promise(function(resolve, reject) {
@@ -37,6 +52,40 @@ function readBlobAsBytes(blob) {
   }
 }
 
+var native = {}
+var keepGlobals = ['fetch', 'Headers', 'Request', 'Response']
+var exercise = ['polyfill']
+
+// If native fetch implementation exists, save it and allow it to be replaced
+// by the polyfill. Native implementation will be exercised additionally.
+if (self.fetch) {
+  keepGlobals.forEach(function(name) {
+    native[name] = self[name]
+  })
+  self.fetch = undefined
+  exercise.push('native')
+}
+
+var slice = Array.prototype.slice
+
+function featureDependent(testOrSuite, condition) {
+  (condition ? testOrSuite : testOrSuite.skip).apply(this, slice.call(arguments, 2))
+}
+
+exercise.forEach(function(exerciseMode) {
+  suite(exerciseMode, function() {
+    if (exerciseMode === 'native') {
+      suiteSetup(function() {
+        keepGlobals.forEach(function(name) {
+          self[name] = native[name]
+        })
+      })
+    }
+
+    var nativeChrome = /Chrome\//.test(navigator.userAgent) && exerciseMode === 'native'
+    var nativeFirefox = /Firefox\//.test(navigator.userAgent) && exerciseMode === 'native'
+    var polyfillFirefox = /Firefox\//.test(navigator.userAgent) && exerciseMode === 'polyfill'
+
 test('resolves promise on 500 error', function() {
   return fetch('/boom').then(function(response) {
     assert.equal(response.status, 500)
@@ -148,7 +197,7 @@ suite('Headers', function() {
       headers.set({field: 'value'}, 'application/json');
     }, TypeError)
   })
-  test('is iterable with forEach', function() {
+  featureDependent(test, !nativeFirefox, 'is iterable with forEach', function() {
     var headers = new Headers()
     headers.append('Accept', 'application/json')
     headers.append('Accept', 'text/plain')
@@ -164,7 +213,7 @@ suite('Headers', function() {
     assert.deepEqual({key: 'accept', value: 'text/plain', object: headers}, results[1])
     assert.deepEqual({key: 'content-type', value: 'text/html', object: headers}, results[2])
   })
-  test('forEach accepts second thisArg argument', function() {
+  featureDependent(test, !nativeFirefox, 'forEach accepts second thisArg argument', function() {
     var headers = new Headers({'Accept': 'application/json'})
     var thisArg = 42
     headers.forEach(function() {
@@ -205,7 +254,7 @@ suite('Request', function() {
     })
   })
 
-  ;(ArrayBuffer in self ? test : test.skip)('sends ArrayBuffer body', function() {
+  featureDependent(test, support.arrayBuffer, 'sends ArrayBuffer body', function() {
     var text = 'name=Hubot'
 
     var buf = new ArrayBuffer(text.length)
@@ -294,7 +343,7 @@ suite('Request', function() {
     })
   })
 
-  ;(/Chrome\//.test(navigator.userAgent) && !fetch.polyfill ? test.skip : test)('construct with used Request body', function() {
+  featureDependent(test, !nativeChrome, 'construct with used Request body', function() {
     var request1 = new Request('https://fetch.spec.whatwg.org/', {
       method: 'post',
       body: 'I work out'
@@ -324,7 +373,7 @@ suite('Request', function() {
     })
   })
 
-  ;(/Chrome\//.test(navigator.userAgent) && !fetch.polyfill ? test.skip : test)('clone with used Request body', function() {
+  featureDependent(test, !nativeChrome, 'clone with used Request body', function() {
     var req = new Request('https://fetch.spec.whatwg.org/', {
       method: 'post',
       body: 'I work out'
@@ -339,7 +388,7 @@ suite('Request', function() {
 
   // https://fetch.spec.whatwg.org/#concept-bodyinit-extract
   suite('BodyInit extract', function() {
-    ;(Request.prototype.blob ? suite : suite.skip)('type Blob', function() {
+    featureDependent(suite, support.blob, 'type Blob', function() {
       test('consume as blob', function() {
         var request = new Request(null, {method: 'POST', body: new Blob(['hello'])})
         return request.blob().then(readBlobAsText).then(function(text) {
@@ -363,7 +412,7 @@ suite('Request', function() {
         })
       })
 
-      ;(Request.prototype.blob ? test : test.skip)('consume as blob', function() {
+      featureDependent(test, support.blob, 'consume as blob', function() {
         var request = new Request(null, {method: 'POST', body: 'hello'})
         return request.blob().then(readBlobAsText).then(function(text) {
           assert.equal(text, 'hello')
@@ -377,7 +426,7 @@ suite('Request', function() {
 suite('Response', function() {
   // https://fetch.spec.whatwg.org/#concept-bodyinit-extract
   suite('BodyInit extract', function() {
-    ;(Response.prototype.blob ? suite : suite.skip)('type Blob', function() {
+    featureDependent(suite, support.blob, 'type Blob', function() {
       test('consume as blob', function() {
         var response = new Response(new Blob(['hello']))
         return response.blob().then(readBlobAsText).then(function(text) {
@@ -401,7 +450,7 @@ suite('Response', function() {
         })
       })
 
-      ;(Response.prototype.blob ? test : test.skip)('consume as blob', function() {
+      featureDependent(test, support.blob, 'consume as blob', function() {
         var response = new Response('hello')
         return response.blob().then(readBlobAsText).then(function(text) {
           assert.equal(text, 'hello')
@@ -450,7 +499,7 @@ suite('Response', function() {
     })
   })
 
-  ;(Response.prototype.arrayBuffer ? test : test.skip)('clone blob response', function() {
+  featureDependent(test, support.blob, 'clone blob response', function() {
     return fetch('/binary').then(function(response) {
       return Promise.all([response.clone().arrayBuffer(), response.arrayBuffer()]).then(function(bufs){
         bufs.forEach(function(buf){
@@ -483,7 +532,7 @@ suite('Response', function() {
 
 // https://fetch.spec.whatwg.org/#body-mixin
 suite('Body mixin', function() {
-  ;(Response.prototype.arrayBuffer ? suite : suite.skip)('arrayBuffer', function() {
+  featureDependent(suite, support.blob, 'arrayBuffer', function() {
     test('resolves arrayBuffer promise', function() {
       return fetch('/hello').then(function(response) {
         return response.arrayBuffer()
@@ -530,7 +579,6 @@ suite('Body mixin', function() {
 
     test('rejects arrayBuffer promise after body is consumed', function() {
       return fetch('/hello').then(function(response) {
-        assert(response.arrayBuffer, 'Body does not implement arrayBuffer')
         assert.equal(response.bodyUsed, false)
         response.blob()
         assert.equal(response.bodyUsed, true)
@@ -541,7 +589,7 @@ suite('Body mixin', function() {
     })
   })
 
-  ;(Response.prototype.blob ? suite : suite.skip)('blob', function() {
+  featureDependent(suite, support.blob, 'blob', function() {
     test('resolves blob promise', function() {
       return fetch('/hello').then(function(response) {
         return response.blob()
@@ -591,7 +639,7 @@ suite('Body mixin', function() {
     })
   })
 
-  ;(Response.prototype.formData ? suite : suite.skip)('formData', function() {
+  featureDependent(suite, support.formData, 'formData', function() {
     test('post sets content-type header', function() {
       return fetch('/request', {
         method: 'post',
@@ -604,7 +652,7 @@ suite('Body mixin', function() {
       })
     })
 
-    test('rejects formData promise after body is consumed', function() {
+    featureDependent(test, !nativeChrome, 'rejects formData promise after body is consumed', function() {
       return fetch('/json').then(function(response) {
         assert(response.formData, 'Body does not implement formData')
         response.formData()
@@ -618,7 +666,7 @@ suite('Body mixin', function() {
       })
     })
 
-    test('parses form encoded response', function() {
+    featureDependent(test, !nativeChrome, 'parses form encoded response', function() {
       return fetch('/form').then(function(response) {
         return response.formData()
       }).then(function(form) {
@@ -649,7 +697,7 @@ suite('Body mixin', function() {
       })
     })
 
-    test('handles json parse error', function() {
+    featureDependent(test, !polyfillFirefox, 'handles json parse error', function() {
       return fetch('/json-error').then(function(response) {
         return response.json()
       }).catch(function(error) {
@@ -746,9 +794,7 @@ suite('Methods', function() {
     })
   })
 
-  var patchSupported = !/PhantomJS/.test(navigator.userAgent)
-
-  ;(patchSupported ? test : test.skip)('supports HTTP PATCH', function() {
+  featureDependent(test, support.patch, 'supports HTTP PATCH', function() {
     return fetch('/request', {
       method: 'PATCH',
       body: 'name=Hubot'
@@ -818,9 +864,7 @@ suite('Atomic HTTP redirect handling', function() {
     })
   })
 
-  var permanentRedirectSupported = !/PhantomJS|Trident/.test(navigator.userAgent)
-
-  ;(permanentRedirectSupported ? test : test.skip)('handles 308 redirect response', function() {
+  featureDependent(test, support.permanentRedirect, 'handles 308 redirect response', function() {
     return fetch('/redirect/308').then(function(response) {
       assert.equal(response.status, 200)
       assert.equal(response.ok, true)
@@ -834,13 +878,11 @@ suite('Atomic HTTP redirect handling', function() {
 
 // https://fetch.spec.whatwg.org/#concept-request-credentials-mode
 suite('credentials mode', function() {
-  var omitSupported = !self.fetch.polyfill
-
   setup(function() {
     return fetch('/cookie?name=foo&value=reset', {credentials: 'same-origin'});
   })
 
-  ;(omitSupported ? suite : suite.skip)('omit', function() {
+  featureDependent(suite, exerciseMode === 'native', 'omit', function() {
     test('request credentials defaults to omit', function() {
       var request = new Request('')
       assert.equal(request.credentials, 'omit')
@@ -916,3 +958,6 @@ suite('credentials mode', function() {
     })
   })
 })
+
+  })
+})
diff --git a/test/worker.js b/test/worker.js
index c31b459858820b00fd6dfb9a8c6b9a180644bf7f..0c826fd09065735fcde33dca07d6f9d79d38ad44 100644
--- a/test/worker.js
+++ b/test/worker.js
@@ -1,13 +1,12 @@
-importScripts('../node_modules/chai/chai.js')
-importScripts('../node_modules/mocha/mocha.js')
+importScripts('/node_modules/chai/chai.js')
+importScripts('/node_modules/mocha/mocha.js')
 
 mocha.setup('tdd')
 self.assert = chai.assert
 
-importScripts('../bower_components/es6-promise/promise.js')
-importScripts('../fetch.js')
-
-importScripts('test.js')
+importScripts('/bower_components/es6-promise/promise.js')
+importScripts('/test/test.js')
+importScripts('/fetch.js')
 
 function title(test) {
   return test.fullTitle().replace(/#/g, '');