include the C++ string library in unit tests

to fix compilation errors in some compilers

include the C++ string library in unit tests
8ec63876 · Hubert Chathi · ea13edca · 8ec63876
Commit 8ec63876 authored 5 years ago by Hubert Chathi
--- a/tests/include/unittest.hh
+++ b/tests/include/unittest.hh
@@ -16,7 +16,7 @@
 #include <iostream>
 #include <iomanip>
 #include <cstdlib>
-
+#include <string>

 std::ostream & print_hex(
    std::ostream & os,