Add Data Saver ChromeDriver test for exp directive protocol.

tools/chrome_proxy/webdriver/bypass.py

Index: tools/chrome_proxy/webdriver/bypass.py
diff --git a/tools/chrome_proxy/webdriver/bypass.py b/tools/chrome_proxy/webdriver/bypass.py
index 6000687d46641bb277526de559b93583de2c2982..d5774dd65a3dc8cfd3ea607771952be4626c8998 100644
--- a/tools/chrome_proxy/webdriver/bypass.py
+++ b/tools/chrome_proxy/webdriver/bypass.py
@@ -135,6 +135,39 @@ class Bypass(IntegrationTest):
       self.assertEqual(1, histogram['count'])
       self.assertIn({'count': 1, 'high': 5, 'low': 4}, histogram['buckets'])
 
+  # Verify that the Data Reduction Proxy understands the "exp" directive.
+  def testExpDirectiveBypass(self):
+    with TestDriver() as test_driver:
+      test_driver.AddChromeArg('--enable-spdy-proxy-auth')
+      test_driver.AddChromeArg('--data-reduction-proxy-experiment=test')
+
+      # Verify that loading a page other than the specific exp directive test
+      # page loads through the proxy without being bypassed.
+      test_driver.LoadURL('http://check.googlezip.net/test.html')
+      responses = test_driver.GetHTTPResponses()
+      self.assertNotEqual(0, len(responses))
+      for response in responses:
+        self.assertHasChromeProxyViaHeader(response)
+
+      # Verify that loading the exp directive test page with "exp=test" triggers
+      # a bypass.
+      test_driver.LoadURL('http://check.googlezip.net/exp/')
+      responses = test_driver.GetHTTPResponses()
+      self.assertNotEqual(0, len(responses))
+      for response in responses:
+        self.assertNotHasChromeProxyViaHeader(response)
+
+    # Verify that loading the same test page without setting "exp=test" loads
+    # through the proxy without being bypassed.
+    with TestDriver() as test_driver:

[megjablon, 2017/03/14 22:22:55]

Rather than using another test driver in another test I did this by:

test_driver._StopDriver()
test_driver.RemoveChromeArg('--data-reduction-proxy-experiment=test')

Not sure which one is better, but we could decide on one to be consistent. 

[sclittle, 2017/03/14 22:48:59]

Good point. @robertogden, WDYT?

I think underscore-prefixed methods are supposed to be used internally within a
class (https://google.github.io/styleguide/pyguide.html?showone=Naming#Naming),
but we could just make StopDriver() public to fix that.

I think I'd still lean towards using a separate TestDriver, since the separate
indentation of each "with" block seems a bit easier to read to me. It also means
that we don't have to individually remove flags that are no longer needed, which
seems a bit simpler.

Using a separate test driver could lead to more duplication if lots of the same
flags are needed each time, but maybe that could be mitigated by making a helper
function that adds the flags that are common to each of those runs.

WDYT?

[Robert Ogden, 2017/03/15 15:43:29]

I agree using a separate 'with' is cleaner, although functionally equivalent.

[sclittle, 2017/03/15 18:01:35]

OK, I'll leave this as-is then. Thanks!

+      test_driver.AddChromeArg('--enable-spdy-proxy-auth')
+
+      test_driver.LoadURL('http://check.googlezip.net/exp/')
+      responses = test_driver.GetHTTPResponses()
+      self.assertNotEqual(0, len(responses))
+      for response in responses:
+        self.assertHasChromeProxyViaHeader(response)
+
 
 if __name__ == '__main__':
   IntegrationTest.RunAllTests()