We present HISTEX, a tool for testing the implementation of isolation levels of relational database management systems. It is a multi-process application and executes input histories in a generic transactional notation on commercial DBMS platforms. HISTEX could be used to discover potential errors in the implementation of Isolation Levels by Relational Database Management Systems or cases where a system behaves over restrictively. It can also be used for performance measurements related to database workloads executing on real database systems instead of simulated environments. HISTEX has been implemented in C by utilizing Embedded SQL. However, many of its ideas could be reincarnated in new implementations that could rely on other database connectivity paradigms such as JDBC, JPA etc. We expect that by presenting some of the ideas behind its development we could re-invigorate some fresh interest and involvement in the research community regarding such tools.