Fix bug when using --continue in the tests (#884)

* Fix bug when using --continue in the tests

* Formatting

test/include/test.hpp

@@ -6,6 +6,7 @@
 #include <functional>
 #include <iostream>
 #include <sstream>
+#include <type_traits>
 #include <unordered_map>
 #include <vector>
 
@@ -101,7 +102,9 @@ inline Stream& operator<<(Stream& s, std::nullptr_t)
     return s;
 }
 
-template <class Stream, class Range>
+template <class Stream,
+          class Range,
+          class = typename std::enable_if<not std::is_convertible<Range, std::string>{}>::type>
 inline auto operator<<(Stream& s, const Range& v) -> decltype(stream_range(s, v.begin(), v.end()))
 {
     s << "{ ";