I came across an amazing presentation years ago (which of course I can't find) that listed a bunch of kinds of failures for remote services that people usually don't test for.<p>In addition to timeout, 3xx, 4xx, 5xx, etc, it listed things like:<p><pre><code> -connection closes after 10 bytes of data
-returns 200 OK but no content (got this one in production today)
-returns contents of www.google.com
-returns contents of /dev/random
-returns contents of /etc/passwd
-returns correctly-formatted unicode chinese text
-returns ansi color control characters
-returns an incorrect content-type, labeled correctly (You requested Content-Type: application/json, I send -back Content-Type: application/jpeg)
-returns one byte of data every 29 seconds
</code></pre>
What are some types of "out-of-band failures" you've encountered that developers don't usually (but should) test for?<p>(extra bonus points if you can find the original presentation)