diff --git a/test/wasi/README.md b/test/wasi/README.md
index 8f37d45..deb9237 100644
--- a/test/wasi/README.md
+++ b/test/wasi/README.md
@@ -2,6 +2,8 @@
 
 ```sh
 wasicc -O3 wasi_printf.c -o wasi_printf.wasm
+wasm-opt -O3 wasi_printf.wasm -o wasi_printf.wasm
+wasm-strip wasi_printf.wasm
 ```
 
 ## Run
diff --git a/test/wasi/wasi_printf.c b/test/wasi/wasi_printf.c
index fccd1cc..5bc173b 100644
--- a/test/wasi/wasi_printf.c
+++ b/test/wasi/wasi_printf.c
@@ -1,9 +1,15 @@
 #include <stdio.h>
 #include <stdint.h>
+#include <string.h>
 #include <time.h>
 
+/*
+ * Helpers
+ */
+
 #define WASM_EXPORT __attribute__((used)) __attribute__((visibility ("default")))
 
+static inline
 struct timespec timespec_diff(struct timespec start, struct timespec end)
 {
   struct timespec temp;
@@ -17,6 +23,11 @@ struct timespec timespec_diff(struct timespec start, struct timespec end)
   return temp;
 }
 
+static inline
+int rand_range(int min, int max){
+   return min + rand() / (RAND_MAX / (max - min + 1) + 1);
+}
+
 WASM_EXPORT
 uint32_t fib(uint32_t n)
 {
@@ -26,25 +37,80 @@ uint32_t fib(uint32_t n)
   return fib(n-1) + fib(n-2);
 }
 
-int main()
-{
-  struct timespec start, finish;
+/*
+ * Tests
+ */
 
-  // Chew up some CPU time
-  volatile int n=38, result;
+static char gString[16];
 
-  printf("Calculating fib(%d)...\n", n);
+__attribute__((constructor))
+void test_init_some_global() {
+  static const char data[] = "Constructor OK\n";
+  memcpy(gString, data, sizeof(data));
+}
 
+void test_constructor() {
+  fwrite(gString, 1, sizeof(gString), stdout);
+}
+
+void test_write() {
+  fwrite("Hello world\n", 1, 12, stdout);
+}
+
+void test_printf() {
+  printf("Hello %s!\n", "printf");
+}
+
+void test_random() {
+  unsigned entropy;
+  getentropy(&entropy, sizeof(entropy));
+  srand(entropy);
+  int x = rand_range(0, 10);
+  int y = rand_range(0, 10);
+  printf("%d + %d = %d\n", x, y, x+y);
+}
+
+void test_gettime() {
+  struct timespec now;
+  clock_gettime(CLOCK_REALTIME, &now);
+  printf("Now: %lld sec, %ld ns\n", now.tv_sec, now.tv_nsec);
+}
+
+void test_fib10() {
+  volatile uint32_t n = 10, result;
+  result = fib(n);
+  printf("fib(%d) = %d\n", n, result);
+}
+
+void test_perf_fib38() {
+  struct timespec start, finish;
+  volatile uint32_t n = 38, result;
+
+  printf("fib(%d) = ", n);
+  fflush(stdout);
+
+  // Chew up some CPU time
   clock_gettime(CLOCK_REALTIME, &start);
   result = fib(n);
   clock_gettime(CLOCK_REALTIME, &finish);
 
   struct timespec delta = timespec_diff(start, finish);
+  unsigned ms = (delta.tv_sec*1000) + (delta.tv_nsec/1000000);
+  printf("%d [%u ms]\n", result, ms);
+}
 
-  printf("Finished in: %lu ms\n", (delta.tv_sec*1000) + (delta.tv_nsec/1000000));
-
-  // TODO: this fails for some reason
-  //printf("Finished in: %lf ms\n", delta.tv_sec*1000.0 + delta.tv_nsec/1000000.0);
+/*
+ * Main
+ */
 
+int main()
+{
+  test_write();
+  test_constructor();
+  test_printf();
+  test_gettime();
+  //test_random();
+  test_fib10();
+  test_perf_fib38();
   return 0;
 }
diff --git a/test/wasi/wasi_printf.wasm b/test/wasi/wasi_printf.wasm
index df44dfe..2cde244 100755
Binary files a/test/wasi/wasi_printf.wasm and b/test/wasi/wasi_printf.wasm differ