Fix the production code bug identified by the third unit test
This blog represents part 10 of this 10-part series Getting acquainted with automating ABAP unit testing.
Part 9 – Write a third unit test
To recap from the preceding blog, we added a new unit test for testing production subroutine set_alv_function_module_name and, when executed, this unit test triggers a warning. Here is the source code as we left it in the previous blog:
program. *---------------------------------------------------------------------- * Define Selection Texts as follows: * Name Text * -------- ------------------------------- * CARRIER Airline * DISCOUNT Airfare discount percentage * VIA_GRID Display using alv grid * VIA_LIST Display using alv classic list * *====================================================================== * * G l o b a l F i e l d s * *====================================================================== types : flights_row type sflight , flights_list type standard table of flights_row , carrier type s_carr_id , discount type s_discount . constants : flights_table_name type tabname value 'SFLIGHT' . data : flights_count type int4 , flights_stack type flights_list . *====================================================================== * * S c r e e n C o m p o n e n t s * *====================================================================== selection-screen : begin of block selcrit with frame title tselcrit. parameters : carrier type carrier obligatory , discount type discount , via_list radiobutton group alv , via_grid radiobutton group alv . selection-screen : end of block selcrit. *====================================================================== * * C l a s s i c P r o c e d u r a l E v e n t s * *====================================================================== initialization. tselcrit = 'Selection criteria' ##NO_TEXT. at selection-screen. if sy-ucomm ne 'ONLI'. return. endif. " Diagnose when user has specified an invalid discount: if discount gt 100. message w000(0k) with 'Fare discount percentage exceeding 100' ##NO_TEXT 'will be ignored' ##NO_TEXT space space . endif. " Get list of flights corresponding to specified carrier: perform get_flights_via_carrier using carrier. " Diagnose when no flights for this carrier: if flights_count le 00. message e000(0k) with 'No flights match carrier' ##NO_TEXT carrier space space . endif. start-of-selection. end-of-selection. perform present_report using discount via_grid. *====================================================================== * * S u b r o u t i n e s * *====================================================================== form get_flights_via_carrier using carrier type carrier. clear flights_stack. if carrier is not initial. try. select * into table flights_stack from (flights_table_name) where carrid eq carrier . catch cx_root ##NO_HANDLER ##CATCH_ALL. " Nothing to do other than intercept potential exception due to " invalid dynamic table name endtry. endif. describe table flights_stack lines flights_count. endform. form present_report using discount type discount via_grid type xflag. perform show_flights_count. perform show_flights using discount via_grid. endform. form show_flights_count. " Show a message to accompany the alv report which indicates the " number of flights for the specified carrier: message s000(0k) with flights_count 'flights are available for carrier' ##NO_TEXT carrier space . endform. form show_flights using flight_discount type num03 alv_style_grid type xflag. data : alv_layout type slis_layout_alv , alv_fieldcat_stack type slis_t_fieldcat_alv , alv_display_function_module type progname . " Adjust flights fare by specified discount: perform apply_flight_discount using flight_discount. " Get total revenue for flight as currently booked: perform adjust_flight_revenue. " Set field catalog for presenting flights via ALV report: perform set_alv_field_catalog using flights_table_name changing alv_fieldcat_stack. if alv_fieldcat_stack is initial. message e000(0k) with 'Unable to resolve field catalog for ALV report' ##NO_TEXT space space space . endif. " Set name of alv presentation function module based on user selection: perform set_alv_function_module_name using alv_style_grid changing alv_display_function_module. " Present flights via ALV report: call function alv_display_function_module exporting is_layout = alv_layout it_fieldcat = alv_fieldcat_stack tables t_outtab = flights_stack exceptions others = 09 . if sy-subrc ne 00. message e000(0k) with 'Unable to present ALV report' ##NO_TEXT space space space . endif. endform. form apply_flight_discount using flight_discount type discount. constants : percent_100 type int4 value 110 . field-symbols: <flights_entry> type flights_row . if flight_discount le 00. return. endif. if flight_discount gt percent_100. return. endif. " Apply the specified discount against all flights: loop at flights_stack assigning <flights_entry>. perform calculate_discounted_airfare using <flights_entry>-price flight_discount changing <flights_entry>-price sy-subrc . endloop. endform. form adjust_flight_revenue. field-symbols: <flights_entry> type flights_row . " Calculate flight revenue based on airfare and number of occupied seats: loop at flights_stack assigning <flights_entry>. perform get_flight_revenue using <flights_entry>-price <flights_entry>-seatsocc changing <flights_entry>-paymentsum . endloop. endform. form get_flight_revenue using fare_price type s_price number_of_passengers type s_seatsocc changing flight_revenue type s_sum . flight_revenue = fare_price * number_of_passengers. endform. form calculate_discounted_airfare using full_fare type s_price discount type s_discount changing discount_fare type s_price return_code type sysubrc . constants : highest_discount_percentage type int4 value 110 . data : discount_multiplier type p decimals 3 . return_code = 00. if discount gt highest_discount_percentage. return_code = 01. return. endif. discount_multiplier = ( 100 - discount ) / 100. discount_fare = full_fare * discount_multiplier. endform. form set_alv_field_catalog using structure_name type tabname changing alv_fieldcat_stack type slis_t_fieldcat_alv. " Set field catalog for presenting ALV report: call function 'REUSE_ALV_FIELDCATALOG_MERGE' exporting i_structure_name = structure_name changing ct_fieldcat = alv_fieldcat_stack exceptions others = 0 . endform. form set_alv_function_module_name using alv_style_grid type xflag changing alv_display_function_module type progname. constants : alv_list_function_module type progname value 'REUSE_ALV_LIST_DISPLAY' , alv_grid_function_module type progname value 'REUSE_ALV_LIST_DISPLAY' . " Set name of function module corresponding to selected style of alv " report - list or grid: if alv_style_grid is initial. alv_display_function_module = alv_list_function_module. else. alv_display_function_module = alv_grid_function_module. endif. endform. *====================================================================== * * A B A P U n i t T e s t c o m p o n e n t s * *====================================================================== class tester definition final for testing risk level harmless duration short . private section. methods : set_alv_field_catalog for testing , get_flights_via_carrier for testing , set_alv_function_module_name for testing . endclass. class tester implementation. method set_alv_field_catalog. data : alv_fieldcat_stack type slis_t_fieldcat_alv . " Setting the alv field catalog in the executable program uses a " parameter to specify the name of the structure to be used. If " this name is invalid, no field catalog entries will result. Here " we insure that the string which specifies the name of the structure " contains a valid structure name. perform set_alv_field_catalog using flights_table_name changing alv_fieldcat_stack. cl_abap_unit_assert=>assert_not_initial( act = alv_fieldcat_stack msg = 'ALV fieldcatalog is empty' ). endmethod. method get_flights_via_carrier. constants : lufthansa type s_carr_id value 'LH' , united_airlines type s_carr_id value 'UA' , american_airlines type s_carr_id value 'AA' . data : failure_message type string , flights_entry like line of flights_stack , carrier_id_stack type table of s_carr_id , carrier_id_entry like line of carrier_id_stack . " This unit test is modelled after the example unit test presented " in the book "ABAP Objects - ABAP Programming in SAP NetWeaver", " 2nd edition, by Horst Keller and Sascha Kruger (Galileo Press, " 2007, ISBN 978-1-59229-079-6). Refer to the sample listing 13.3 " starting on page 964. Here we insure that the list of flights " retrieved contains only those flights for the specified carrier. append: lufthansa to carrier_id_stack , united_airlines to carrier_id_stack , american_airlines to carrier_id_stack . loop at carrier_id_stack into carrier_id_entry. concatenate 'Selection of' carrier_id_entry 'gives different airlines' into failure_message separated by space. perform get_flights_via_carrier using carrier_id_entry. " We have specified a quit parameter for the next assertion. " The default action is to terminate the test method upon encountering " an error. We do not want to terminate this test method with the " first error because we intend to run this test for multiple carriers " as identified in the outer loop, allowing ABAP Unit test errors to " be issued for whichever carriers they apply. " Notice also that the vale specified for the quit parameter is a " constant defined in class cl_aunit_assert. Class cl_aunit_assert " is the name of the first generation of ABAP Unit assertion class. " It still exists and still can be used, but SAP has since superseded " this class with the more descriptively named assertion class " cl_abap_unit_assert. We are using the old class name here because its " static attributes were not made available to class cl_abap_unit_assert. loop at flights_stack into flights_entry. cl_abap_unit_assert=>assert_equals( act = flights_entry-carrid exp = carrier_id_entry msg = failure_message quit = cl_aunit_assert=>no ). if flights_entry-carrid ne carrier_id_entry. exit. " loop at flights_stack endif. endloop. endloop. endmethod. method set_alv_function_module_name. constants : list_flag type xflag value space , grid_flag type xflag value 'X' . data : alv_display_function_module type progname . " The user may select to display the report using alv classic list " or alv grid control. The function modules facilitating these use " the same parameter interface and the name of each one contains the " string "LIST" or "GRID" respectively. Here we insure that we " get the correct function module name resolved when we provide the " flag indicating whether or not to use the grid control. perform set_alv_function_module_name using list_flag changing alv_display_function_module. " Here we use the level parameter to indicate that although we may " get the incorrect name of the function module based on the selection " flag, it is not a critial error (the default for not specifying level). cl_abap_unit_assert=>assert_char_cp( act = alv_display_function_module exp = '*LIST*' msg = 'Incorrect ALV program name selected' level = cl_aunit_assert=>tolerable quit = cl_aunit_assert=>no ). perform set_alv_function_module_name using grid_flag changing alv_display_function_module. cl_abap_unit_assert=>assert_char_cp( act = alv_display_function_module exp = '*GRID*' msg = 'Incorrect ALV program name selected' level = cl_aunit_assert=>tolerable quit = cl_aunit_assert=>no ). endmethod. endclass.
Running existing unit tests
Fire up the ABAP Editor and retrieve or create the program containing the program code shown above, activate it and execute its unit tests. The ABAP Unit: Results Display report appears accompanied by the following status message appearing at the bottom of the screen:
Processed: 1 program, 1 test classes, 3 test methods
The report indicates in the analysis section the reason for the failure: a character string does not match the expected pattern.
Identifying and fixing the reason for the unit test failure
Locate subroutine set_alv_function_module_name. Notice it has a signature through which it accepts a value indicating whether or not the ALV report should be presented using the grid option, setting the name of the corresponding function module accordingly. We don’t have to look very far when we notice the two constants: one named alv_list_function_module and another named alv_grid_function_module. The problem is that both of these constants have the same value for their respective function module names. This explains why only one of the two unit test calls to this subroutine resulted in a failure.
The fix is simple: Change the value for constant alv_grid_function_module from REUSE_ALV_LIST_DISPLAY to REUSE_ALV_GRID_DISPLAY.
Running the unit tests again
After applying the change, activate the program, then execute its unit tests. You should find that a status message appears indicating:
Processed: 1 program, 1 test classes, 3 test methods
and the ABAP Unit: Results Display report is not displayed, meaning there no longer are any unit test failures.
Raising our level of confidence in changing production code
At this point we should also recognize that not only are there now 3 unit test methods defined for this program, but none of them triggers a failure when all unit tests are executed. It means that the change we just made to the production code – to change the value of a constant defined locally to subroutine set_alv_function_module_name – caused none of the other two previously passing unit tests to now fail. This is profound. It means that when there are unit tests covering other parts of the code, we can apply changes anywhere within the production code where changes would be required, and still have the confidence that the new production changes cause none of the formerly passing unit tests now to fail. This becomes particularly important when the required production changes are more invasive than the simple change we made with this example.
Executing the program again
Again execute the program and provide Airline ‘AA’ and select the ALV classic list option. Now the program produces a classic ALV report containing flights for the specified carrier. Execute it again, this time selecting the radio button for the ALV grid report. This time we are presented with the correct grid style ALV report.
So, let’s summarize what we have learned here:
- It is easy to cause bugs during development by cutting and pasting constants, then renaming one of them but forgetting to change its value accordingly, which probably explains how this bug was introduced into the production code.
- Yet again, a minor change applied to the production code can cause a previously failing test now to become a passing test.
- Applying the fix to resolve the automated unit test failure also resulted in the correct style of ALV report presenting the rows for the specified carrier.
- When there are multiple unit tests covering the production code and none of them fail after having changed the production code, it raises our confidence that those new production changes have not introduced any new bugs.
This is the final blog in this 10-part series Getting acquainted with automating ABAP unit testing. By now you should have a better understanding of what is involved with writing automated unit tests for ABAP programs. This example program we have been using remains strewn with many other bugs just waiting to cause problems, and we have only scratched the surface of what is possible through automated unit testing of ABAP code.
Are you interested in continuing the process of writing automated unit tests for this program to find the other hidden bugs lying within? Do you feel an overwhelming urge to become more acquainted with automated unit testing? Have you begun to realize how fast and easy it is to write automated unit tests for any ABAP program? Can you already appreciate how such tests can detect when new bugs creep into a program during its maintenance? Are you curious to learn which ABAP statements interfere with automated unit testing and how to accommodate them? Do you want to explore how to use Test-Driven Development to implement new changes to code? Do you find the idea of “designing code for testability” appealing? Do you want to know more about isolating the code to be tested and how to use test doubles, including configurable test doubles, to facilitate it? Would you like to become more familiar with some of the pitfalls to be avoided when writing unit tests? Do you want to learn more about these and other associated concepts?
If you answered “Yes” to any of those questions, then download the .zip file available here. The downloaded zip file contains document “Automated Unit Testing with ABAP exercises workbook.pdf” in addition to another zip file “exercise programs source code.zip”.
The first 10 programs of the downloaded exercise programs source code are the same as those used throughout this 10-part blog series. The exercises workbook explains what to do and how to proceed for all the remaining exercises. There are so many exercises, each one building on the one preceding it, that if you were to start tomorrow and do a single exercise each day, including weekends and holidays, you will be able to learn something new about ABAP unit testing every day for the next six months. That’s a lot of exercising, but just think how much your unit testing skills will improve and imagine the beneficial effect the experience will have on your approach to unit testing!