User:Sam/Arch testing

Notes on arch testing.

Avoiding common failures

 * Use the  locale:

A not-insignificant number of test suites assume this US locale. Sometimes the failure is as "simple" as collation issues (e.g. sorting depending on region -- which would only show up if you're using a non-Western locale), but often, tests specifically request en_US.UTF-8, and hence fail immediately when it's not available.


 * Use TZ=UTC:

It's recommended to use a time namespace and set TZ=UTC to avoid unexpected offsets affecting tests.