This directory contains API coverage tests of POSIX IO. This is loosely defined as the set of functions that fdio implements. The goal is to test the error cases of each of these functions. It is not a test of the underlying RIO transport or backing filesystems.
Note that POSIX stipulates that “if more than one error occurs in processing a function call, any one of the possible errors may be returned, as the order of detection is undefined.” The tests in this directory test our implementation of POSIX, and not the spec itself. For example, we check that
openat(not_a_directory, "", O_RDONLY)
returns ENOENT, rather than it returning one of ENOENT or ENOTDIR, both of which could apply.