Proper unit testing requires covering all program paths. This is difficult without deep
program knowledge and analysis. The automatic test data generation (TDG) feature in IBM Test
Accelerator for Z utilizes symbolic execution and generates data for hard-to-reach program paths,
accelerating unit test code coverage.
Automatic test data generation overview
Symbolic execution is a powerful technique used in software testing and analysis. Instead of
executing a program with concrete input values, symbolic execution operates on symbolic values,
which represent all possible values that a variable can take. During symbolic execution, the
program's control flow and data dependencies are tracked symbolically, allowing for the exploration
of multiple execution paths simultaneously.
Automatic test data generation uses symbolic execution to update the possible values in the form
of constraints for all relevant variables on the semantics.
In the program CHKREC(See Figure 1), X and Y are input parameters, and Figure 2 is a Control Flow
Graph for CHKREC. There are four possible execution paths in the program.
IF X<Y THEN and IF X>30 THEN
IF X<Y THEN and IF X>30 ELSE
IF X<Y ELSE and IF X>30 THEN
IF X<Y ELSE and IF X>30 ELSE
When TDG generates test data of the execution path(2), the total conditional expression is X<Y
and NOT(Y-X+10>30), and X=10 and Y=20 is a satisfiable solution. There are alternative satisfiable
solutions like X=5 and Y=18, X=25 and Y=36. Therefore, you might get different values each TDG
action.Figure 1. Program CHKREC Figure 2. Control Flow Graph for CHKREC
Test data generation based on a recorded test
You can generate test data for hard-to-reach paths after recording a happy path through the
program. In this example, assume that TEST1 was created from a recording. After
running TEST1, you can see the code that is not covered. In Figure 3, you’ll
see three branches of EVALUATE are not covered.Figure 3. Three branches of
EVALUATE are not covered
Also, “WRITE-ERROR-MESSAGE” paragraph to write an error message is not covered by TEST1. (See
Figure 4)Figure 4. WRITE-ERROR-MESSAGE paragraph to write an error message is
not covered by TEST1
Now we assume that you want to create test data for the “When Other” alternative path shown in
Figure 3. Open the test case (.tc) file, Select
Start Test Data Generation from the context menu of TEST1 to generate
PathInfo0, and change the value of SQLCODE in the SQL SELECT statement to guide Automatic Test Data
Generation to “WHEN OTHER” branch. (See Figure 5).Figure 5. Change the value
of SQLCODE
Automatic Test Data Generation generates a new test for the alternate path guided by user input
data. In this program, when SQLCODE is not 0, “WRITE-ERROR-MESSAGE” paragraph will be executed.
Automatic Test Data Generation will generate test data for these three CICS statements(ASKTIME,
FORMATTIME, and LINK).
The generated data is affected by the variable referenced in conditional branch and recorded
data. Here, the value of DFHEIBLK in EXEC CICS LINK comes from the recorded data of DFHEIBLK in
PROCEDURE DIVISION. (See Figure 6)Figure 6. Value of DFHEIBLK
WS-TIME and WS-DATE are not referenced in any conditional branch. Random values are generated
complying with the data attribute for these parameters.Figure 7. Random
values are generated
