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26 June 2012

Perceptual Diffs

I showed how perceptual diffs are core to our team's continuous deployment during my Ignite talk at Velocity.

The gist:
  1. On every commit we build and push to staging, which takes ~8 minutes
  2. We screenshot each staging version and compare it visually to the live version on known URLs
  3. When staging and live versions differ, we get an email

Example 1: Fixing a typo. I can't see the difference. Computers can.

Example 2: Histogram axis regression. One of the first where we caught a bug before pushing it to users.

Perceptual diffs have closed the loop on continuous deployment, giving us the confidence to push new code more often.

Hopefully they put the Ignite video up somewhere~

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