add split string function

tests/split_str.cpp

@@ -4,10 +4,10 @@
 
 #include "string/string.hpp"
 
-using v_str = std::vector<std::string>;
 
-TEST(split_str, check__func)
+TEST(split_str, check)
 {
-  // v_str res {"asdf","qwer","zxcv"};
-  // ASSERT_EQ(tools::func::split_str("asdf,qwer,zxcv", ','), res);
+  hack::v_str v { "asdf", "qwer", "zxcv" };
+
+  ASSERT_EQ(hack::split_str("asdf,qwer,zxcv", ','), v);
 }