Poudriere
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222095
#FreeBSD ports maintainers ought to be required to use poudriere to test their updates before they are accepted. There are few things more annoying than building a set of packages only to discover that one has an unsatisfied dependency that the maintainer did not notice.
When building on the “plain” system, any dependencies installed for any given port remain installed. A later port build can then – usually through autoconf – detect and use them.
In poudriere, each build starts with a “clean” environment, and if a port does not declare a dependency, it does not have the package available.
The Porters’ Handbook currently mentions poudriere, but there is no requirement to use it.
Examples: