Experiment 2:
Code without explicit invariants
•563-line C program: regular expression search & replace [Hutchins][Rothermel]
•Task: modify to add Kleene +
•Complementary use of both detected invariants and traditional tools (such as grep)
This is realistic code.

The program has been used in testing research, so it comes with a good test suite.

Be explicit:
2 programmers in the study
they were my co-authors -- not me.
I provided the Daikon output, then was completely hands off

[Maybe mention that more details are available in my ICSE 99 paper.]

The program author didn’t waste any of those 563 lines on comments.
I decided that adding Kleene + was a useful and realistic task.
I provided the programmers  with the detected invariants, and also permitted them their usual debugging and code understanding tools.  (They often found themselves using those instead of the invariants:  invariants aren’t the panacea for all software engineering tasks.)
“Traditional tools”:  Be specific about what the programmers did:  eyeballed the code; grep; search.  (Ran the program?)