tests refactoring

tests/utils.h

@@ -1,4 +1,15 @@
 #pragma once
 
+#include <string>
+#include<cstddef>
+
+std::size_t count_lines(const std::string& filename);
+
 void prepare_logdir();
 
+std::string file_contents(const std::string& filename);
+
+std::size_t count_lines(const std::string& filename);
+
+std::ifstream::pos_type filesize(const std::string& filename);
+