ref. https://github.com/boostorg/test/commit/235acea2fa4b1eb7580acbfcce94d696c86bb207#diff-9131a06d2a1a6d0c877c9b7909acbbde

Olivier Stasse authored 4 years ago and olivier stasse committed 4 years ago

This command is used to display some information in a ostream and get
back a string.
Add an unit-test to verify it.
Additionnally the unit-test improves makeCommandReturnType.