as(): Fix tests and update validator

[akarnokd]

Here is a patch for your PR regarding as().

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (z/as@c1f26ee). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             z/as       #2   +/-   ##
=======================================
  Coverage        ?   96.28%           
  Complexity      ?     5831           
=======================================
  Files           ?      634           
  Lines           ?    41633           
  Branches        ?     5761           
=======================================
  Hits            ?    40087           
  Misses          ?      612           
  Partials        ?      934

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