tests: improve diagnostics when asserting empty files

* tests/chmod/c-option.sh: Use `compare /dev/null ... || fail=1`
rather than `test -s ... && fail=1`, so that the file contents
are output, thus improving diagnostics for failing tests.
* tests/cp/acl.sh: Likewise.
* tests/cp/cp-a-selinux.sh: Likewise.
* tests/cp/cp-mv-enotsup-xattr.sh: Likewise.
* tests/cp/reflink-perm.sh: Likewise.
* tests/dd/misc.sh: Likewise.
* tests/misc/env-null.sh: Likewise.
* tests/misc/env.sh: Likewise.
* tests/misc/nice.sh: Likewise.
* tests/misc/nohup.sh: Likewise.
* tests/misc/printenv.sh: Likewise.
* tests/misc/xattr.sh: Likewise.
* tests/mv/update.sh: Likewise.
* tests/rm/deep-2.sh: Likewise.
* tests/rm/read-only.sh: Likewise.
* tests/split/r-chunk.sh: Likewise.
* tests/tail-2/follow-stdin.sh: Likewise.
* tests/tail-2/inotify-race.sh: Likewise.
* tests/tail-2/wait.sh: Likewise.
* tests/touch/no-dereference.sh: Likewise.

* cfg.mk (sc_prohibit_test_empty:): New syntax-check.
* tests/cp/proc-zero-len.sh: Adjust to avoid false syntax-check failure.
* tests/cp/proc-zero-len.sh: Likewise.
* tests/mv/part-symlink.sh: Likewise.
* tests/tail-2/infloop-1.sh: Likewise.

6 files changed, 13 insertions, 13 deletions

diff --git a/tests/misc/env-null.sh b/tests/misc/env-null.sh
index 6544fb37b..9b9c95e73 100755
--- a/tests/misc/env-null.sh
+++ b/tests/misc/env-null.sh
@@ -40,7 +40,7 @@ compare out1 out2 || fail=1
 # env -0 does not work if a command is specified.
 env -0 echo hi > out
 test $? = 125 || fail=1
-test -s out && fail=1
+compare /dev/null out || fail=1
 
 # Test env -0 on a one-variable environment.
 printf 'a=b\nc=\0' > exp || framework_failure_
@@ -53,7 +53,7 @@ env "$(printf 'a=b\nc=')" printenv -0 a > out || fail=1
 compare exp out || fail=1
 env -u a printenv -0 a > out
 test $? = 1 || fail=1
-test -s out && fail=1
+compare /dev/null out || fail=1
 env -u b "$(printf 'a=b\nc=')" printenv -0 b a > out
 test $? = 1 || fail=1
 compare exp out || fail=1
diff --git a/tests/misc/env.sh b/tests/misc/env.sh
index 877a5e35e..c4b97377a 100755
--- a/tests/misc/env.sh
+++ b/tests/misc/env.sh
@@ -25,11 +25,11 @@ print_ver_ env
 a=1
 export a
 env - > out || fail=1
-test -s out && fail=1
+compare /dev/null out || fail=1
 env -i > out || fail=1
-test -s out && fail=1
+compare /dev/null out || fail=1
 env -u a -i -u a -- > out || fail=1
-test -s out && fail=1
+compare /dev/null out || fail=1
 env -i -- a=b > out || fail=1
 echo a=b > exp || framework_failure_
 compare exp out || fail=1
diff --git a/tests/misc/nice.sh b/tests/misc/nice.sh
index 8efb7d87d..26a01ca9f 100755
--- a/tests/misc/nice.sh
+++ b/tests/misc/nice.sh
@@ -81,12 +81,12 @@ if test x$(nice -n -1 nice 2> /dev/null) = x0 ; then
   if test -w /dev/full && test -c /dev/full; then
     nice -n -1 nice > out 2> /dev/full
     test $? = 125 || fail=1
-    test -s out && fail=1
+    compare /dev/null out || fail=1
   fi
 else
   # superuser - change succeeds
   nice -n -1 nice 2> err || fail=1
-  test -s err && fail=1
+  compare /dev/null err || fail=1
   test x$(nice -n -1 nice) = x-1 || fail=1
   test x$(nice --1 nice) = x-1 || fail=1
 fi
diff --git a/tests/misc/nohup.sh b/tests/misc/nohup.sh
index 2328b43e2..b3f4274ce 100755
--- a/tests/misc/nohup.sh
+++ b/tests/misc/nohup.sh
@@ -73,7 +73,7 @@ if test -w /dev/full && test -c /dev/full; then
   nohup echo hi 2> /dev/full
   test $? = 125 || fail=1
   test -f nohup.out || fail=1
-  test -s nohup.out && fail=1
+  compare /dev/null nohup.out || fail=1
   rm -f nohup.out
   exit $fail
 ) || fail=1
@@ -86,7 +86,7 @@ if test -t 1; then
   # It must exist.
   test -f nohup.out || fail=1
   # It must be empty.
-  test -s nohup.out && fail=1
+  compare /dev/null nohup.out || fail=1
 fi
 
 cat <<\EOF > exp || fail=1
@@ -106,7 +106,7 @@ if test -t 1; then
   # It must exist.
   test -f nohup.out || fail=1
   # It must be empty.
-  test -s nohup.out && fail=1
+  compare /dev/null nohup.out || fail=1
 fi
 
 cat <<\EOF > exp || fail=1
diff --git a/tests/misc/printenv.sh b/tests/misc/printenv.sh
index fb911d004..054b02c25 100755
--- a/tests/misc/printenv.sh
+++ b/tests/misc/printenv.sh
@@ -37,7 +37,7 @@ fi
 # Printing a single variable's value.
 env -- printenv ENV_TEST > out
 test $? = 1 || fail=1
-test -s out && fail=1
+compare /dev/null out || fail=1
 echo a > exp || framework_failure_
 ENV_TEST=a env -- printenv ENV_TEST > out || fail=1
 compare exp out || fail=1
@@ -76,6 +76,6 @@ compare exp out || fail=1
 # Bug present through coreutils 8.0.
 env a=b=c printenv a=b > out
 test $? = 1 || fail=1
-test -s out && fail=1
+compare /dev/null out || fail=1
 
 Exit $fail
diff --git a/tests/misc/xattr.sh b/tests/misc/xattr.sh
index 269424611..f208090f5 100755
--- a/tests/misc/xattr.sh
+++ b/tests/misc/xattr.sh
@@ -66,7 +66,7 @@ getfattr -d c >out_c || skip_ "failed to get xattr of file"
 grep -F "$xattr_pair" out_c || fail=1
 
 # cp's -a option must produce no diagnostics.
-cp -a a d 2>err && test -s err && fail=1
+cp -a a d 2>err && { compare /dev/null err || fail=1; }
 getfattr -d d >out_d || skip_ "failed to get xattr of file"
 grep -F "$xattr_pair" out_d || fail=1