diff --git a/c-programming/io/freadln.c b/c-programming/io/freadln.c
index 6f7c867..36a0ea2 100644
--- a/c-programming/io/freadln.c
+++ b/c-programming/io/freadln.c
@@ -4,6 +4,9 @@
  * The `freadln` function reads a line from STDIN into a string, allocating
  * memory for it.
  *
+ * NOTE: Test: Declare macro POSIX when compiling if you're using a POSIX
+ * system.
+ *
  * TODO: Figure out potential problems
  * TODO: Add 'flushing' of STDIN (while there are characters, read them) before
  * the input reading loop to avoid input queues
@@ -76,7 +79,11 @@ int freadln(FILE* f, char** output, size_t* length_out) {
 }
 
 #ifdef TEST
-# if defined(_WIN32) || defined(WIN32)
+# if POSIX
+#  include <unistd.h>
+#  define SLEEP_FN sleep
+#  define DO_SLEEP 1
+# elif defined(_WIN32) || defined(WIN32)
 #  include <windows.h>
 #  define SLEEP_FN(x) Sleep((DWORD) x)
 #  define DO_SLEEP 1