my GeeCON 2014 "lightning talk" about custom assertions

1. Custom Assertions
...when assertEquals() is not enough
Tomek Kaczanowski

2. freegreatpicture.com
A 15 minutes
„lightning talk”

3. ●
Developer
●
Blogger
●
Books author
twitter: @tkaczanowski
http://practicalunittesting.com
Tomek Kaczanowski

7. Expectations
our tests should:
●
verify
americanmethod.com

8. Expectations
our tests should:
●
verify
●
be readable
code.tutsplus.com

9. Expectations
our tests should:
●
verify
●
tell a story
jasonfurnell.wordpress.com

10. Expectations
our tests should:
●
verify
●
tell a story
●
be focused
noble.org

11. Expectations
our assertions should:
●
verify
●
tell a story
●
be focused

12. The Evolution of Assertions

13. The Evolution of Assertions

14. The Evolution of Assertions

15. The Evolution of Assertions

16. The Evolution of Assertions

17. Talk is cheap.
Show me the code.

18. assertThat(...)

19. assertThat(...)

20. assertThat(...)

21. The Anatomy of Custom Assertion

22. The Anatomy of Custom Assertion

23. The Anatomy of Custom Assertion

24. Custom Assertions or Private Methods?
verifySuccessfulRedirect(response, FALLBACK_URL);
dashboardShows(dashboardPage, „my campaign”,
„Target”, „PL”);
noHits(„2007-06-06 02:00”);
noHits(„2007-06-06 03:00”);
hitsAndRevenue(„2007-06-06 04:00”, 2, 7);
...

25. Real Life Examples

26. Real Life Examples
actual

27. Real Life Examples
actual
assertThat(found)
.overwritingErrorMessage(
„expected row for {} but found only rows for {}”
stringDate, dates(actual)
)
.isTrue();

28. Real Life Examples
actual

29. Conclusions

30. Upsides
●
readable
●
reusable
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simple to write
●
cheap to maintain

31. Upsides and Downsides
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need to write them
●
can hide bad smells
●
readable
●
reusable
●
simple to write
●
cheap to maintain

32. Best Practices
use AssertJ
• forget about JUnit/TestNG assertions
introduce custom assertions
• when private methods are not good
enough
• if you care about ubiquitous language
• when “then” part is getting huge
• to impress/confuse your team mates

33. The Evolution of Assertions

34. The Evolution of Assertions

35. Links
AssertJ: http://joel-costigliola.github.io/assertj/
tools used to prepare these slides
• http://shaky.github.bushong.net/
• http://hilite.me/
• http://asciiflow.com

36. Thank you!
You can learn more about
writing high quality tests by
reading my books:
„Practical Unit Testing”
and
„Bad Tests, Good Tests”.
Please visit
http://practicalunittesting.com
to learn more.