Steps and Decisions taken to built junit4git, a tool to support impact testing in JVM projects.

1. IMPACT TESTING
RAQUEL PAU

2. STOP WASTING TIME
FOR UNRELATED TESTS

5. TEST IMPACT REPORT

6. HOW CAN WE BUILD REPORTS
PER INDIVIDUAL TESTS ?
- THROUGH A JUNIT LISTENER
Me
TEXTO

7. TEXTO
JUNIT LISTENERS
▸ Receive notifications when a test starts or ends.
▸ It is an agnostic JVM language solution
▸ It is not necessary create a build tool plugin
▸ It is not necessary change our tests
▸ We can use multiple Listeners per application
simultaneously. != for Runners.

8. JUNIT LISTENERS

9. TEXTO
JUNIT5 CONFIGURATION EXAMPLE

10. TEXTO
DEMO
▸ git clone https://github.com/rpau/junit4git.git
▸ gradle check
▸ As it is - Run all the tests
▸ Without changes (again) - Skip all the tests
▸ With changes - Run the affected tests

11. WERE CAN I STORE THE TESTS
TO COMPARE WITH?
- AS A HIDDEN GIT NOTE
Me
TEXTO

12. TEXTO
GIT NOTES BENEFITS
▸ We do not need a server
▸ They are optionally fetched
▸ They are references to commits
▸ Like Gerrit does with SCA tools ;)
export GIT_NOTES_REF=refs/notes/tests
git notes show

13. HOW ARE WE NOTIFIED WHEN
A CLASS IS LOADED?
- USING A INSTRUMENTATION
Me
TEXTO

14. TEXTO
JAVA AGENTS FOR INTRUMENTING CODE
▸ It is the same solution than code coverage tools apply.
▸ Implementing a ClassFileTransformer you can implement:
▸ We get notifications when a class is loaded (once for the
whole test suite).
protected byte[] instrumentClass(String name, byte[]
classfileBuffer)

15. BUT AGAIN: WE NEED TO
BE NOTIFIED PER TEST!

16. TEXTO
IMPACT REPORT GENERATION WORKFLOW
▸ Listener notifies the agent when a test T starts
▸ The JVM notifies the agent when a new class C is loaded
▸ The agent modifies the class C constructors to get notified
when a new instance is created.
▸ The test creates an object. The agent becomes notified
and stores that C is used in T.
▸ Listener notifies the agent when the test T finishes.

17. HOW DO WE DYNAMICALLY
MODIFY CODE?
- WITH JAVASSIST
Me
TEXTO

18. TEXTO
WE NEED TO DINAMICALLY MODIFY CODE
▸ In class constructors to notify the agent
▸ In test class to add the @Ignore when it is necessary.
▸ and.. these modifications should:
▸ Not be persistent
▸ Be JVM Language agnostic

20. Questions?