* https://www.in-ulm.de/~mascheck/various/ash/
And Wikipedia does not say that. It says that the Minix Almquist shell, specifically, had a non-conformant test utility. The Almquist shell did not, after all, have a built-in test command at all to start with, so the standard conformance of that utility wasn't a matter for the Almquist shell.
Once again Wikipedia is wrong, because Thomas Dickey's original page that purportedly supports this claim points out that the Minix test command was an external command and not part of the Almquist shell. M. Dickey even pointed to the source code for the external command on GitHub.
* https://invisible-island.net/autoconf/portability-test.html#...
* https://github.com/Stichting-MINIX-Research-Foundation/minix...
* https://commons.wikimedia.org/wiki/File:Don't%20abbreviate%2...
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Most shells needed updates to fully-conform with the POSIX standard. The wiki mentions that the Almquist shell did not implement a "test" program that fully conformed.
The sh-posix on HP-UX also had subtle changes to the ksh88 source to bring it into compliance (but this shell still supported arrays and coprocesses).
https://en.wikipedia.org/wiki/Almquist_shell