GB1479122A - Method of operating a computer to produce test case programmes - Google Patents

Abstract

1479122 Generating test case programs for testing computers INTERNATIONAL BUSINESS MACHINES CORP 11 Dec 1975 50745/75 Heading G4A A method of operating a computer to produce test case programs, written in a predetermined computer language, which are suitable for checking the operation of computer programs, comprises entering into the computer information relating to the frequency in which particular types of instructions are to appear in a test case program and the total number of instructions which are to so appear; operating the computer to generate instructions having a frequency of type and a total number conforming with the entered information, to predict the results of the execution of each generated instruction including any resultant changes to the test case program's variables to reject any generated instruction that would cause an unwanted interrupt during execution of the test case program, and to generate error checking code for inclusion in the test case program, the code including instructions for checking the flow of execution and for checking the calculated values of the variables against their predicted values; and storing the generated test case program in a form suitable for further use by a computer. Prediction of changes in a test case program's variables may be by way of creation of a dictionary entry for each variable declared in a generated program and maintaining an updated -value for a variable each time it is used in the generated program. The dictionary may be stack-organized according to data type; if a data item is an array the array and its associated status flags are stored elsewhere than in the dictionary and are addressed via the dictionary entry. As described the computer language is PL/1 and details of the generation of IF and DO instructions thereof are given. Generation of particular types of instructions is on a random basis. For example, in an ASSIGNMENT instruction the l.h.s. or target is obtained by selecting randomly a variable from a dictionary stack, and the r.h.s. by calling a subroutine EXPRESSION GENERATOR which generates a random expression and the predicted value thereof. Expression generation is achieved by way of creation, using recursive routines, of a tree structure of operators and operands, evaluation of the predicted value of the generated expression being achieved by list processing of the tree structure. The error checking code includes instructions which call error routines whenever a failure is detected during the execution of a test case program, and automatically generated comments may be inserted in the test case program to aid the tracing of such failures. Following the generation of a test case program a PRINT routine reorders the program, if necessary, prior to its storage for further use by a computer. The test case programs may be used for checking the operation of a compiler.