People often ask what are the differences between RBUs and VUs. Obviously RBUs are more realistic while VUs are the perfect vehicle for testing APIs, but here is a table giving you a breakdown.
| Feature | RBU | VU |
|---|---|---|
| Threads | 6 threads downloading data in parallel | Single thread downloading data in sequence |
| Ajax | Native support and simple to implement | Can be scripted but takes time |
| Flash | Has ability to test Flash interaction | Flash objects can be downloaded, but won’t be played |
| Reporting | Screen-shot of failed page captured; error codes from server | Content of last requested object captured; error codes from server |
| Max Throughput | 768KBytes/sec per request (up to 15 requests per browser) | 100KBytes/sec per virtual user |
Some things to take note of:
- There is a difference in the difficulty for scripting RBUs vs. VUs. RBU scripts are easier to create with the Selenium IDE tool and have validation built in. Because RBUs mimic human behavior the
scripts include built-in validation concepts. For example an error will be thrown if you try to click on an element that doesn’t exist because the page being displayed is a “server too busy” page instead of the expected page. With VUs, you have to code in your own validation logic. - VUs are the preferred way to test SOAP/REST and other “non-browser” HTTP requests.
- Often the right approach involves using a bit of both RBUs and VUs. The VUs can be used to lay down base load on “read-only” pages that don’t involve form interaction or AJAX. The 80/20 rule applies here, you can generate 80% of the read-only traffic with VUs and use RBUs for the remaining 20%.
We hope this give you a better understanding of the differences and relative strengths of RBUs and VUs.
http://www.merriam-webster.com/dictionary/concurrent
“Single thread downloading data concurrently”
I think you mean “sequentially”, not “concurrently”.
Earl
Earl,
Thanks for the note – we’ve corrected that typo and updated the content of this post to reflect some of the latest info on our product.
Patrick Lightbody
Founder, BrowserMob