test-functions: account for the potential absence of test(1) as a builtin

Presently, the test_whenceforth() function potects itself from being
adversely affected by printf(1) not being a builtin utility. Consider
the following test.

PATH=.
whenceforth -x newer/file

Owing to the modification of PATH, it becomes impossible to execute any
of the standard utilities unless they happen to be builtins. The
workaround is to temporarily define printf as a function which duly
executes the external utility.

Having run the test suite with the yash shell, it has served as a sharp
reminder that one cannot assume that test(1) is always available as a
builtin either. In fact, yash implements test(1) as a "substitutative
built-in command". Below is the relevant material from its manual.

- https://magicant.github.io/yash/doc/builtin.html#types
- https://magicant.github.io/yash/doc/exec.html#search
- https://magicant.github.io/yash/doc/index.html#builtins

It is a curious thing, to say the least. Essentially, substitutative
builtins can only be used for as long as an executable of the same name
can be found in PATH. Since the purpose of test_whenceforth() is not to
directly evaluate the behaviour of the test(1) utility, this commit
implements the same safeguard for test(1) as is present for printf(1).

Signed-off-by: Kerin Millar <kfm@plushava.net>
Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 9 insertions, 5 deletions

diff --git a/test-functions b/test-functions
index c96ac48..7c848c1 100755
--- a/test-functions
+++ b/test-functions
@@ -687,14 +687,17 @@ test_whenceforth() {
 		else
 			test_description="PATH=${path} whenceforth $(quote_args "$@")"
 			(
-				# If necessary, conduct the test with a printf
-				# function in effect, duly covering shells that
-				# do not implement it as a builtin. Otherwise,
-				# it could become unavailable on account of the
-				# various values of PATH being tested.
+				# If necessary, declare functions to cover the
+				# utilities that might otherwise be unavailable
+				# on account of the various values of PATH
+				# being tested. It cannot be assumed that the
+				# utilities in question are builtins.
 				case ${printf_cmd} in
 					/*) printf() { "${printf_cmd}" "$@"; }
 				esac
+				case ${test_cmd} in
+					/*) test() { "${test_cmd}" "$@"; }
+				esac
 				# shellcheck disable=2030
 				PATH=${path}
 				whenceforth "$@" >/dev/null
@@ -703,6 +706,7 @@ test_whenceforth() {
 	}
 
 	printf_cmd=$(command -v printf)
+	test_cmd=$(command -v test)
 	iterate_tests 5 "$@"
 }