Research And Implementation Of Automated Testing For IEC 61131-3 ST Language

As the core equipment of the industrial control system,the programmable logic controller(PLC)has been widely used in various automation control fields.PLC is essentially a computer dedicated to industrial control,which can adapt to complex industrial environments.With the increasing scale of PLC software and the increasing number of PLC equipment,many problems have broken out in reality,which can result in economic losses and even personal safety issues.Therefore,people pay more and more attention to the correctness and security of PLC software,especially the software used on military equipment.The IEC 61508 standard clearly states that PLC software must be thoroughly tested regarding function,structure,and safety before being released.With the widespread use of PLCs,there have been some integrated development environments for editing PLC software and simulators that simulate PLC execution behavior.However,the software testing methods of these PLC tools are mainly based on the test cases that are manually set and input,mainly concerned with the needs of users.This method is not only unable to be well automated but also cannot provide information about code coverage.Therefore,it is urgent to develop an automated test tool for PLC software.The first process of software testing is to design test cases for the software under test,but this process requires a lot of labor and is very time-consuming.Testers are often required to understand the requirements specifications and program structure in order to design high-quality test cases.In this study,we solved the test case generation problem of the structured text(ST)programming language in the IEC 61131-3 PLC standard.ST is a high-level text programming language for complex algorithmic operations.We propose a framework and some algorithms for automated generation of test cases for the IEC 61131-3 ST language,using dynamic symbolic execution techniques combined with satisfiability modulo theories.We applied this method to implement a coverage-based automated test case generation tool STAutoTester.The tool can generate a multi-cycle test sequence every iteration,and the test coverage set with maximum coverage can be obtained after multiple iterations.We conducted a lot of experiments to evaluate STAutoTester.The experimental results show that STAutoTester can effectively generate test cases.The test case set has a high coverage rate and a small number;the test case generation time is short,and the cost is reduced;the test process does not require manual intervention,and the degree of automation is high.It can play an active role in large-scale,logically complex software.