tests/tests.h: add ARRAY_SIZE and LENGTH_OF macros

* tests/tests.h (ARRAY_SIZE, LENGTH_OF): New macros.
* tests/aio.c (ARRAY_SIZE): Remove.
* tests/mmsg.c (LENGTH_OF): Remove.
diff --git a/tests/aio.c b/tests/aio.c
index 29d2191..5335a26 100644
--- a/tests/aio.c
+++ b/tests/aio.c
@@ -42,8 +42,6 @@
  && defined __NR_io_destroy
 # include <linux/aio_abi.h>
 
-# define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
-
 int
 main(void)
 {
diff --git a/tests/mmsg.c b/tests/mmsg.c
index ba6cfe4..fe758a7 100644
--- a/tests/mmsg.c
+++ b/tests/mmsg.c
@@ -45,8 +45,6 @@
 };
 # endif
 
-# define LENGTH_OF(arg) ((unsigned int) sizeof(arg) - 1)
-
 static int
 send_mmsg(int fd, struct mmsghdr *vec, unsigned int vlen, unsigned int flags)
 {
diff --git a/tests/tests.h b/tests/tests.h
index de8302a..c55b329 100644
--- a/tests/tests.h
+++ b/tests/tests.h
@@ -66,6 +66,9 @@
 /* Make a hexdump copy of C string */
 const char *hexdump_strdup(const char *);
 
+# define ARRAY_SIZE(arg) ((unsigned int) (sizeof(arg) / sizeof((arg)[0])))
+# define LENGTH_OF(arg) ((unsigned int) sizeof(arg) - 1)
+
 # define SKIP_MAIN_UNDEFINED(arg) \
 	int main(void) { error_msg_and_skip("undefined: %s", arg); }