Discuss Legacy Code and the different approaches to get it under control. Discuss different methods for testing, Unit Tests with ABAP Test Seams. Discuss Software Exploration Tools, Moose2Model, SAP2Moose

1. Legacy Code
Unit Test
ABAP Test Seams
Storing the mental Model
Referent: Rainer Winkler
Date: 07 October 2017

3. Legacy Code
code without tests
Michael Feathers
Read the book „Working effectively with Legacy Code“ by Michael Feathers

4. Andrea Goulet
Read for instance this article https://t.co/XkvBBPixVe

5. Legacy Code is code with
too many code smells

6. Code Smell

7. Code Smell –
something that
makes work difficult

8. Duplicated code
Wrong names
Overcomplicated design
Too many branches or loops
Too long methods
...

9. Depends on the project, the
developer and the usage

10. Fail fast -> Reduce costs to
handle errors
• Error messages
• ASSERT statements
• Logging

11. Write down customer
requirements
• Use a requirement engineering tool
• Use a simple Excel sheet with unique ID´s for each
requirement

12. Do not focus only on
performance
• Field-Symbols are fast, but make coding also harder to
maintain

13. Use TDD for utility coding
• To specify how it works
• Because noone is able to test all using applications if
changes are required
TDD - Test Driven Design

14. Find solutions for smells that hurt

15. Do not apply design rules that add
complexity without sufficient
benefit

16. Source: Rainer Winkler

17. No medicine without prescription

18. Is it worth the effort to design software well?
https://martinfowler.com/bliki/DesignStaminaHypothesis.html

19. Is it worth the effort to design software well?
https://martinfowler.com/bliki/DesignStaminaHypothesis.html
Legacy code

20. What to do?

21. Clean Code

22. Write automatic tests

23. Clean Code
If we design well,
the machine will work well

24. Write automatic tests
If we test well,
we stop working when all
tests are passed

25. Clean Code

26. Write automatic tests
Source https://mix.msfc.nasa.gov/abstracts.php?p=2869

27. Use a combination of Clean Code
and automatic tests

28. Decide which approach is best

29. Typical workflow while
changing Legacy Code

30. Typical workflow while
changing Legacy Code
1 Add Unit test to
- understand
- have a safety belt

31. Typical workflow while
changing Legacy Code
1 Add Unit test to
- understand
- have a safety belt
2 Refactor to simplify changes

32. Typical workflow while
changing Legacy Code
1 Add Unit test to
- understand
- have a safety belt
2 Refactor to simplify changes
3 Change Unit test so that it passes
only after changes are made

33. Typical workflow while
changing Legacy Code
1 Add Unit test to
- understand
- have a safety belt
2 Refactor to simplify changes
3 Change Unit test so that it passes
only after changes are made
4 Make changes in the code

34. Unit Tests
Why?

35. Unit Test to understand

36. Unit Test as
characterization test

37. Unit Test to
documentate

38. Integration tests
check for correctness

39. Only an Integration Test can
make sure that everything
works as required

40. • Do not make too many Unit Tests
• Try to documentate the logic
• New Unit Tests should add a new aspect
• Use good names for the tests
Tips

41. Demo 1

42. Unit Test with dependencies

43. Add mock instances in tests

44. But

45. ABAP Objects is not designed
for many method calls like JAVA

46. https://help.sap.com/doc/abapdocu_750_index_htm/7.50/en-US/index.htm
ABAP - Keyword Documentation → ABAP Programming Guidelines → Architecture → Object-Oriented Programming → Modularization

47. Is this one of the reasons
people at SAP invented
Test Seams?

48. Tips – Test Seams

49. Read scn blogs

50. Use local class for testing with static public attributes
Can be used in Unit test and in the injected code
Can not be used in the productive code (as FOR TESTING)
How to inject variable values?

51. Define a local class for testing
with static public attribute
Empty Seam at place to be checked
Set attribute in injection
Check for value
How to check whether a code snippet is executed?

52. In earlier releases I often failed to
write Unit Test for typical ABAP
code.
It was too complex and risky

53. With ABAP 7.50 I am normally
successfull.
Test Seams make writing Unit Test easier

54. I use Test Seams when they help
for old and for new coding

55. This tests are also on Github
https://github.com/RainerWinkler/ABAP-Unit-Test-Demo
Synchronized with abapGit (Why not? „Install abapGit make a fork and make a pull request to this“):

56. Why you shouldn't interrupt
a programmer
Jason Heeris

57. Jason Heeris

58. Jason Heeris

59. Jason Heeris

60. Jason Heeris

61. Jason Heeris

62. Jason Heeris

63. Jason Heeris

64. Jason Heeris

65. Can we materialize
the mental model?
or at least a significant part of it?

66. Make sketches with plantUML
Pro:
Easy to do
Con:
Analyzing the code is timeconsuming
Becomes outdated if logic changes
Dependencies of methods do not fit to UML class diagram

67. SAP2Moose and
Moose2Model

68. SAP2Moose
• Extracts meta information to Moose
• Does not extract source code
• Easy to install (A single report)
• Developed using abapGit
• An example of real ABAP Legacy Code, and how it is handled

69. Ask me:
Rainer Winkler
A force layout diagram in Moose
of a real customer code

71. SAP2Moose
Multilevel Usage since 0.4.0

72. Moose2Model
Pro
• Designed to be used by Developers working with Legacy Code
• Displays not only ABAP classes but also tables, WebDynpro ABAP, SAP BW...
• Jump into ABAP Eclipse with ADT Links possible
• Can be adapted
• Diagrams can be customized, elements can be commented
• Changes can be stored
Con
• Requires a separate Smalltalk virtual machine
• Not finished

73. Ask me:
Rainer Winkler
A Moose2Model diagram of a
complete application

75. Ask me:
Rainer Winkler
A Moose2Model diagram of a
part of an application

77. Demo 2

81. Save layout information
to use it later

82. resembles this part of the cartoon

83. Have fun 
moose2model.org
sap2moose.org
sourcetrail.com
Twitter: @moose2model