More tests.

test/util.cc

@@ -26,8 +26,21 @@
  */
 
 #include "util.h"
+#include <cstdarg>
+#include <cstdio>
 #include <cstring>
 
+#ifdef _MSC_VER
+# define vsnprintf vsprintf_s
+#endif
+
+void SPrintf(char *buffer, const char *format, ...) {
+  std::va_list args;
+  va_start(args, format);
+  vsnprintf(buffer, BUFFER_SIZE, format, args);
+  va_end(args);
+}
+
 void Increment(char *s) {
   for (int i = static_cast<int>(std::strlen(s)) - 1; i >= 0; --i) {
     if (s[i] != '9') {