tests: Fix a couple of imports in tests

Fohlen · kjellahl · commit 8d7e37ed33ab · 2019-01-02T15:14:31.000+01:00
See pull request libsigcplusplus#15
diff --git a/tests/test_tuple_cdr.cc b/tests/test_tuple_cdr.cc
@@ -16,6 +16,7 @@
 
 #include <cassert>
 #include <cstdlib>
+#include <string>
 #include <sigc++/tuple-utils/tuple_cdr.h>
 #include <functional>
 
diff --git a/tests/test_tuple_end.cc b/tests/test_tuple_end.cc
@@ -16,6 +16,7 @@
 
 #include <cassert>
 #include <cstdlib>
+#include <string>
 #include <sigc++/tuple-utils/tuple_end.h>
 #include <functional>
 
diff --git a/tests/test_tuple_start.cc b/tests/test_tuple_start.cc
@@ -16,6 +16,7 @@
 
 #include <cassert>
 #include <cstdlib>
+#include <string>
 #include <sigc++/tuple-utils/tuple_start.h>
 #include <functional>
 
