Browser performance tests through selenium

There is a possibility to get closer to what browser-perf is doing by collecting the chrome performance logs and analyzing them.

To get performance logs, turn on performance logs by tweaking loggingPrefs desired capability:

from selenium import webdriver
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities

caps = DesiredCapabilities.CHROME
caps['loggingPrefs'] = {'performance': 'ALL'}
driver = webdriver.Chrome(desired_capabilities=caps)

driver.get('https://stackoverflow.com')

logs = [json.loads(log['message'])['message'] for log in driver.get_log('performance')]

with open('devtools.json', 'wb') as f:
    json.dump(logs, f)

driver.close()

At this point, devtools.json file would contain a bunch of trace records:

[
  {
    "params": {
      "timestamp": 1419571233.19293,
      "frameId": "16639.1",
      "requestId": "16639.1",
      "loaderId": "16639.2",
      "type": "Document",
      "response": {
        "mimeType": "text/plain",
        "status": 200,
        "fromServiceWorker": false,
        "encodedDataLength": -1,
        "headers": {
          "Access-Control-Allow-Origin": "*",
          "Content-Type": "text/plain;charset=US-ASCII"
        },
        "url": "data:,",
        "statusText": "OK",
        "connectionId": 0,
        "connectionReused": false,
        "fromDiskCache": false
      }
    },
    "method": "Network.responseReceived"
  },
  {
    "params": {
      "timestamp": 1419571233.19294,
      "encodedDataLength": 0,
      "requestId": "16639.1"
    },
    "method": "Network.loadingFinished"
  },
  ..
]

Now, the question is, what to do with it.

One option that was initially suggested during the Google Test Automation Conference is to submit the logs to webpagetest.org. There is an example in java available here, but, at the moment, I had no luck implementing it in Python.

In theory, the UI report generated by webpagetest.org would look like this:

enter image description here

They also provide the metrics in JSON/XML and other formats that can be further analyzed.

This is really something, thanks to Vivek Singh for the pointing comment.


browser-perf also uses the logging functionality to pick up the tracing logs, and analyzes the data.

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