Chapter
+5
REGRESSION
+TEST
+
+Regression +testing is the process of validating modified parts of the software, hoping +that the modification does not introduce errors that were not exists before the +modification. An important different between regression testing and development +testing is that during the process of the regression test, a set of established +tests can be reused. Regression test cases is a set of test case aiming at +testing the core function or procedure of the software; core function means +where procedure call with known input is made and the output of the function +will be compare with output the developer expect. The set of test cases will +then be reused for later development as incremental process, as development +gets progress the size of the regression test will also be increase. In other +word, the regression test result in greater test coverage, having greater +coverage will eliminate the amount of errors/bugs in the end product, which is +the ultimate goal of having test cases. Another advantage of the regression +test is that all the tests are automated; all the test cases that gather before +will be run all together without manually inputting date and comparing the +output. These can significantly increase the efficiency of the testing process +in developing a software product.
+ +The +simplest regression test strategy is retest all, when regression +test is started it re-run all the test cases that the test suite have, having +this approach comes in a huge cost in terms of time. In a commercial software +source code can reach up to several millions lines of source code and several +hundred thousands of procedure, having a set of test testing all of these +procedures each time when there is a modification of the software may require +unexpected amount of time. An alternative approach is to have regression +test selection, unlike retest all use all the test cases where as +this approach will use some selection techniques to select a set of test case +to be used. Using this regression test technique, time can be save but having +this approach will also have some negative aspects, for example, the cost of +regression test technique can be high if sophisticate technique were used, +where as low cost with a low quality technique, and the selection may discard +test cases that could expose errors, in other word reducing the fault detection +effectiveness.�
+ +Before +discussing the techniques for regression test selection, we should notice that +during the development process specification of the software may be change, if +the specification has changed it is necessary to remove those test cases that +were reflecting the old specification from the test suite before perform +regression test selection. This is important because if we cannot correctly +determine the test case is out of date or not, we cannot correctly determine +the correctness of the test cases.
+ +
Regression Test Selection Technique
+
+Before +discussing some different types of techniques, it is helpful to have some +notation defined first:
+ +Let +P be a procedure or program; let P� be a modified version of P; and let T be a +test suite for P. T� is a subset of T, and set of test cases to execute on P�
+ +These +techniques discuss below has been discuss in [2]�
+ +�
+Minimization
+Techniques: This technique involve selecting a minimal set of test cases from T
+which cover the modified section of P, P'. In a sample scene, it require T' to
+at least one test case to cover those area where modification had made.
�
+Dataflow
+Techniques: This technique select test case that exercise data interaction that
+have been affected by the modifications.
�
+Safe
+Techniques: Most regression test selection is considered to be not safe; not
+safe means that the selection fail to select those test cases that would reveal
+a error in the modified program. With safe regression test selection
+techniques, it is guarantee that the selection T' (subset of T) would contain
+all the test case in the original test suite T that able to reveal errors in
+P'.
�
+Random
+Techniques: As the name shown, test cases is randomly select from T.
�
+Retest
+All Techniques: The Retest All techniques simply re-use all the test case
+against P'.
Regression
+Test on OpenACS Calendar
+
+The regression test selection
+techniques that have chosen is Retest All, the main disadvantage of this
+technique is that if it run against large software having several thousands
+functions, the time it needs to complete the test is enoumes and the computing
+power it needs is very expensive. But in terms of coverage Retest All
+provide the maximum coverage out of those techniques discuss in the previous
+section; again, having better coverage means the tested software will more
+likely to discover errors before the software go into production. With OpenACS
+Calendar, it is a relative small program with less than 50 functions and less
+than 3000 lines of source code, therefore it is crucial to use the Retest
+All technique in order to achieve the best possible result; to find errors
+as many as possible during the test phase. As we have discuss in the beginning
+of this chapter regression test should be automated, one of the tools provided
+in OpenACS called aa-test [5], it is a tool kit which allow developer to
+register test cases (this require developer to program how to test a piece of
+code and the expected result, the expected result will be compare against the
+actual result) with the system, this tool will build up all the test cases that
+registered, then developer have choice to run all test case in once or select
+individual test case.� Result will be
+available to view on the browser and result statistics will also be logged. We
+have chose to use this automated test tool as out regression test tool. A
+sample regression test case is shown below in Figure 10. A complete regression
+test source code on OpenACS Calendar is attached in the Appendix C.
+
+
+
+
+
+
+
+
+
+
+ 
+ +
Figure 1� the input arguments and return of function cal_item_create
+ +
Figure
+2. regression test
+case for testing function cal_item_create