diff --git a/tests/threaded.c b/tests/threaded.c
index 9761e63..67f3f54 100644
--- a/tests/threaded.c
+++ b/tests/threaded.c
@@ -3,24 +3,63 @@
 #include <stdlib.h>
 #include <threads.h>
 
-static void print_str(char *str) {
+static void print_string_n(char *str, u64 len) {
+    fwrite(str, 1, len, stdout);
+}
+static void print_char(char c) {
+    print_string_n(&c, 1);
+}
+static void print_string(char *str) {
     int str_len = 0;
     while(str[str_len] != 0) {
-        ++str_len;
+        str_len += 1;
     }
-    fwrite(str, 1, str_len, stdout);
+    print_string_n(str, str_len);
 }
 
+static void print_int(i64 number) {
+    if(number < 0) {
+        print_char('-');
+        number = -number;
+    }
+    char buf[20];
+    buf[19] = 0;
+    char *p = buf + sizeof buf - 1;
+    do {
+        *--p = (number%10) + '0';
+        number /= 10;
+    } while(number > 0);
+    print_string(p);
+}
+
+volatile i64 counter = 0;
+
 int thrd_func(void *arg) {
-    print_str("child thread: ok!\n");
+    print_string("child thread: ok!\n");
+    for(int i = 0; i < 100000; ++i) {
+        counter += 1;
+    }
+    print_string("child thread: counter = ");
+    print_int(counter);
+    print_char('\n');
     for(;;);
     return 0;
 }
 
 int main() {
-    print_str("main thread: before\n");
+    print_string("main thread: before\n");
     thrd_t thrd;
-    thrd_create(&thrd, thrd_func, NULL);
-    print_str("main thread: after!\n");
+    int status = thrd_create(&thrd, thrd_func, NULL);
+    if(status == thrd_error) {
+        print_string("main thread: error creating child thread\n");
+        return 1;
+    }
+    print_string("main thread: after!\n");
+    for(int i = 0; i < 100000; ++i) {
+        counter += 1;
+    }
+    print_string("main thread: counter = ");
+    print_int(counter);
+    print_char('\n');
     return 0;
 }