diff --git a/tests/string_test.cpp b/tests/string_test.cpp
index 73c94c6..f1ac9dd 100644
--- a/tests/string_test.cpp
+++ b/tests/string_test.cpp
@@ -173,7 +173,7 @@
   const size_t MAX_LEN;
   Character *ptr, *ptr1, *ptr2;
   size_t n;
-  int len[ITER + 1];
+  size_t len[ITER + 1];
 
  private:
   Character *glob_ptr, *glob_ptr1, *glob_ptr2;
@@ -186,7 +186,7 @@
     n = 0;
     len[n++] = 0;
     for (size_t i = 1; i < ITER; ++i) {
-      int l = (int) exp(log((double) MAX_LEN) * i / ITER);
+      size_t l = static_cast<size_t>(exp(log(static_cast<double>(MAX_LEN)) * i / ITER));
       if (l != len[n - 1]) {
         len[n++] = l;
       }
@@ -392,7 +392,7 @@
       }
       state.ptr1[state.len[i] - 1] = '\0';
 
-      int pos = random() % state.MAX_LEN;
+      size_t pos = random() % state.MAX_LEN;
       char* expected;
       if (pos >= state.len[i] - 1) {
         if (seek_char == 0) {
@@ -421,7 +421,7 @@
       state.ptr1[state.len[i] - 1] = '\0';
       state.ptr2[state.len[i] - 1] = '\0';
 
-      int pos = 1 + (random() % (state.MAX_LEN - 1));
+      size_t pos = 1 + (random() % (state.MAX_LEN - 1));
       int actual;
       int expected;
       if (pos >= state.len[i] - 1) {
@@ -510,7 +510,7 @@
       state.ptr2[state.MAX_LEN - 1] = '\0';
       memcpy(state.ptr, state.ptr2, state.MAX_LEN + state.len[i]);
 
-      int pos = random() % state.MAX_LEN;
+      size_t pos = random() % state.MAX_LEN;
       memset(state.ptr1, '\3', pos);
       state.ptr1[pos] = '\0';
       if (pos < state.len[i]) {
@@ -604,7 +604,7 @@
       state.ptr1[state.len[i] - 1] = '\0';
       state.ptr2[state.len[i] - 1] = '\0';
 
-      int pos = 1 + (random() % (state.MAX_LEN - 1));
+      size_t pos = 1 + (random() % (state.MAX_LEN - 1));
       int actual;
       int expected;
       if (pos >= state.len[i] - 1) {
@@ -722,7 +722,7 @@
       }
       state.ptr1[state.len[i] - 1] = '\0';
 
-      int pos = random() % state.MAX_LEN;
+      size_t pos = random() % state.MAX_LEN;
       char* expected;
       if (pos >= state.len[i] - 1) {
         if (seek_char == 0) {
@@ -749,7 +749,7 @@
 
       memset(state.ptr1, ~seek_char, state.len[i]);
 
-      int pos = random() % state.MAX_LEN;
+      size_t pos = random() % state.MAX_LEN;
       char* expected;
       if (pos >= state.len[i]) {
         expected = NULL;
@@ -780,7 +780,7 @@
 
       memset(state.ptr1, ~seek_char, state.len[i]);
 
-      int pos = random() % state.MAX_LEN;
+      size_t pos = random() % state.MAX_LEN;
       char* expected;
       if (pos >= state.len[i]) {
         expected = NULL;