Beyond Unit Testing

Transcript

1. UNIT TESTING BEYOND
2. THE PYRAMID OF TESTS HAVE YOU SEEN THIS IMAGE BEFORE? ▸ Common knowledge? ▸ Some say that it means that you should write more unit tests than any other type ▸ Another interpretation is that unit tests are faster, and cheaper
3. MOST UNIT TESTING IS WASTE? WHAT IF I TELL YOU
4. ABOUT HOW WE UNIT TEST LET’S BE HONEST
5. LET’S BE HONEST ABOUT HOW WE UNIT TEST WE ONLY TEST PARTIAL VALUES ▸ It would be impossible to test every possible output with every combination of the environment ▸ The combinatory of all those possibilities can easily go up to trillions of things to test
6. LET’S BE HONEST ABOUT HOW WE UNIT TEST WE THINK COVERING ALL LINES IS ENOUGH ▸ Covering all lines is not enough, because not all possible combinations are covered ▸ We like to trick the system by breaking functions to smaller pieces so we can cover all the lines ▸ This makes certain functions or classes more difficult to read
7. LET’S BE HONEST ABOUT HOW WE UNIT TEST WE WOULD RATHER NOT THINK ▸ We find workarounds to make tests pass ▸ If a failing test does not match our understanding, we just change it so that it passes
8. LET’S BE HONEST ABOUT HOW WE UNIT TEST TESTS ARE ALSO CODE ▸ Code needs to maintained ▸ Code contains bug ▸ Tests are code ▸ Your tests need maintenance and also have bugs ▸ Many changes in code need coordinated changes in tests ▸ In many code bases there are more lines of tests than application code
9. BE HUMBLE ABOUT WHAT YOUR UNIT TESTS CAN ACHIEVE James Coplien LET’S BE HONEST ABOUT HOW WE UNIT TEST
10. WITH CONFIDENCE HOW CAN WE REDUCE WASTE
11. REDUCING WASTE WITH CONFIDENCE FOCUS ON INFORMATION AND RISK ▸ Unit tests are meant to reduce the risk of deploying bad code in production ▸ You need information in order to reduce risk ▸ Tests that never fail are not contributing any information
12. DELETE TESTS THAT HAVE NOT FAILED IN A YEAR, MAINTAINING THEM IS COSTLIER James Coplien REDUCING WASTE WITH CONFIDENCE
13. TYPE A QUOTE HERE. DELETE TESTS THAT ONLY TEST THE OBVIOUS
14. TYPE A QUOTE HERE. DELETE TESTS THAT DON’T BREAK AFTER CHANGING THE BEHAVIOUR OF THE CODE THEY TEST
15. TYPE A QUOTE HERE. DELETE TESTS THAT FAIL AND YOU CANNOT UNDERSTAND THE BUSINESS VALUE THEY PROVIDE
16. THE BULK OF UNITS TEST SHOULD BE FOR ALGORITHMS WHERE THERE IS AN INDEPENDENT ORACLE FOR SUCCESS James Coplien REDUCING WASTE WITH CONFIDENCE
17. CONVERT UNIT TESTS TO ASSERTIONS
18. HAVE MORE INTEGRATION AND SYSTEM TESTS
19. WRITE THE DOCUMENTATION BEFORE YOU IMPLEMENT
20. USE PHPSTAN AND PSALM MANY UNIT TESTS CAN BE REPLACED BY BETTER TYPING