Andreas Zeller

IEEE Computer Society Harlan D. Mills Award and Talk by Andreas Zeller Should Computer Scientists Experiment Less? On the past, present, and future of software engineering research

IEEE Computer Society Harlan D. Mills Award and Talk by @andreaszeller.bsky.social

Should Computer Scientists Experiment Less? On the past, present, and future of software engineering research

More information at conf.researchr.org/details/icse...

"Should Computer Scientists Experiment Less?" This is the title of my upcoming Harlan D. Mills Award Talk at ICSE 2026 on the past, present, and future of Software Engineering research. Looking forward to lots of productive discussions!
conf.researchr.org/details/icse...

Mining metrics to predict component failures | Proceedings of the 28th international conference on Software engineering

Impact award! I am happy to report that my ICSE 2006 paper "Mining metrics to predict component failures," with Nachi Nagappan and Thomas Ball, has been selected to receive a retrospective ICSE SEIP Most Influential Paper Award. Read it here: dl.acm.org/doi/10.1145/...

Over the past decade, the automated generation of test inputs has made significant advances. Modern fuzzers and test generators easily produce complex input formats that do systematically cover the input and execution space. Testing protocols, though, has remained a frontier for automated testing, as a test generator has to interact with the program under test, producing messages that conform to the current state of the system. In this paper, we introduce language-based protocol testing, the first approach to specify, automatically test, and systematically cover the full state and input space of protocol implementations. We specify protocols as interaction grammars—an extension of context-free grammars that tag each message element with the communication party that is in charge of producing it. Interaction grammars embed classical state models by unifying states, messages, and transitions all into nonterminals, and can be used for producing interactions as well as parsing them, making them ideally suited for testing protocols. Additional constraints over grammar elements allow us to specify and test semantic features such as binary message formats, checksums, encodings, and the many ways that message features induce states and vice versa. To evaluate the effectiveness of language-based protocol testing, we have implemented it as part of the FANDANGO test generator. We specify several protocols as interaction grammars, including features such as human-readable interactions (SMTP), bit-level encodings (DNS), and dynamic port assignments (FTP), and use them to test the corresponding protocol implementations. By systematically covering the interaction grammar and solving the associated constraints, FANDANGO achieves comprehensive coverage of the protocol interactions, resulting in high code coverage and a thorough assessment of the program under test.

With more and more AI-generated code, comprehensive system testing becomes more important than ever. Our new paper "Language-Based Protocol Testing" (with Alexander Liggesmeyer and Pepe Zamudio), shows how to specify and test all details of how programs interact: arxiv.org/abs/2509.20308

On my way to Savannah, Georgia to an IFIP WG 4.3 meeting, where I’ll present our work on Parameterized Compiler Testing (a joint work with my fantastic co-workers Addison Crump and Alexi Turcotte)

#Fandango 1.1 is now available! With this release, #Fandango becomes a full-fledged _protocol fuzzer_, happily exploring states and messages of protocols such as FTP or DNS. Thanks to José. Valentin, Alexander, and Marius for their hard work!
Find Fandango at fandango-fuzzer.github.io

Andreas Zeller and PhD students

About time: A multi-celebration for becoming a member of Academia Europaea, my SIGSOFT Influential Educator Award, my 60th birthday, becoming an IEEE Fellow, _and_ getting the 2026 IEEE Harlan D. Mills Award. With cake and fizzy drinks!

Starting this year, I will only review for conferences that get rid of a "bidding" phase, as allowing reviewers to bid on papers they want to review opens too many opportunities for manipulation and collusion. For details, see andreas-zeller.info/2025/12/07/R... #nobidding

I am happy to report that I have been named the recipient of the

2026 Harlan D. Mills award

"For sustained contributions to software debugging, program analysis, mining software repositories, and automated test generation." This is a big award – thanks to all!
www.computer.org/volunteering...

Fault localization aims to identify code regions responsible for failures. Traditional techniques primarily correlate statement execution with failures; however, program behavior involves diverse execution features, including variable values, branch conditions, and definition-use pairs, which can provide richer diagnostic insights. This paper comprehensively investigates execution features for fault understanding, addressing two complementary goals. First, we conduct an empirical study of 310 bugs across 20 projects, analyzing 17 execution features and assessing their correlation with failure outcomes. Our findings suggest that fault localization benefits from a broader range of execution features: (1) Scalar pairs exhibit the strongest correlation with failures; (2) Beyond line executions, def-use pairs and functions executed are key indicators for fault localization; and (3) Combining multiple features enhances effectiveness compared to relying on individual features. Second, building on these insights, we introduce a debugging approach that learns relevant features from labeled test outcomes. The approach extracts fine-grained execution features and trains a decision tree to differentiate passing and failing runs. The trained model generates fault diagnoses that explain the underlying causes of failures. Our evaluation demonstrates that the generated diagnoses achieve high predictive accuracy. These interpretable diagnoses empower developers to debug software efficiently by providing deeper insights into failures.

How do execution features relate to failures? In this new ACM TOSEM paper, Marius Smytzek, Martin Eberlein, Lars Grunske, and I analyze which execution features beyond code coverage correlate best with failures and lead to accurate explanations of failure causes: dl.acm.org/doi/10.1145/...

Four hours later, I _think_ I have fixed things again - reinstalled Python and all its packages, rebuilt Spotlight and Mail indexes, cleared macOS caches, subscribed to Creator Studio, and now back to these lost mails… Today I hate you, Apple.

* Mail has lost all my emails sent since Monday
* Mail search is broken too
* Search in reminders cannot find anything
* New Keynote is full of ads!?
* Invoke Python-3.13, get 3.14 instead - venvs are messed up
* LaTeX "minted" crashes (likely b/c Python)

So glad I'm an expert in debugging /sarcasm

Fuzzing software becomes much more effective if you can generate _valid_ inputs. We have now built the first approach to _statically_ extract complete and precise input grammars from parser code, producing syntactically valid and diverse inputs by construction. Enjoy! dl.acm.org/doi/10.1145/...

After a visit to Max Planck Institute for Security and Privacy (MPI-SP) in Bochum, seeing my awesome colleagues @thorstenholz.bsky.social, @mboehme.bsky.social, Mathias Payer, and many more, now on my way to Paris to celebrate ten years of @softwareheritage.org with the great Roberto Di Cosmo

Correction: It's 2,000+ *en*-dashes ("--"), but actually 5,800 *em*-dashes ("---")

$ cd ~/Papers/ $ grep -e '[ ~]-- ' */*.tex | wc -l 2258 $

A researcher used more than 2,000 em-dashes in his papers, revealing AI-based manipulation in 400+ papers since 1985. Professor Zeller claims he "typed" these dashes into the paper by using "two hyphens" and a "typesetting" system.

Fun fact: This is my tenth test of time award :-) We will give a keynote at the FSE 2026 conference. @acm.org @sigsoft.bsky.social

Happy New Year! I am thrilled to report that Jacek Śliwerski, Tom Zimmermann, and I won the ACM SIGSOFT 2026 Impact Award 🏆 for "When do changes induce fixes?" (MSR 2005). The paper introduced the popular SZZ algorithm for linking change histories and bug databases: dl.acm.org/doi/10.1145/...

Problem: Reviewers did not read the paper.
Solution: Write a detailed rebuttal and point to all the places in the paper that answer their questions.
New problem: Reviewers did not read the rebuttal.

IPN Colloquium 15 12 2025 Andreas Zeller YouTube video by IPN (ICT Research Platform Nederland)

The talk is now online:

* Video: www.youtube.com/watch?v=tBO_...
* Slides: andreas-zeller.info/assets/Shoul...

Enjoy! -- Andreas

IPN Colloquium 15 12 2025 Andreas Zeller YouTube video by IPN (ICT Research Platform Nederland)

In an IPN vision talk last Monday, I sketched how future AI "super-coders" would learn from their own experiments with software to far surpass current LLM-based AI coders.

The talk is now online. Enjoy!

* Recording: www.youtube.com/watch?v=tBO_...
* Slides: andreas-zeller.info/assets/Shoul...

Today at 16:00 CET, I'll give a vision talk "Should AI Coders Experiment More?", paving the way to AI “super coders” that may become way more competent than the most experienced programmers - and also way more competent than any LLM-based coders. Details here: ict-research.nl/2025/11/ipn-...

Time to get serious again. New blog post "Reviewer-Author Collusion Rings and How to Fight Them": andreas-zeller.info/2025/12/07/R...

Oops - Of course, Helmut Kohl was chancellor until *1998*, not 1988. Apologies!

A description of the items shown in the LaTeX Korrektor background: * Diomidis Spinellis
, Author of
 “Advice for writing LaTeX documents” * LaTeX 2ε 
Cheat Sheet * Helmut Kohl
, German Chancellor
 1982–1988 * A fictitious
 event poster "Lack Leder LaTeX, Hamburg" * A fictitious
 LaTeX 
propaganda 
poster

Bonus material for The LaTeX Korrektor! Some of you asked: "What are these photos and posters in the background?" Here they come, enlarged and with some details. Enjoy! #LaTeX #LaTeXKorrektor

In case you missed it, watch all six episodes of the LaTeX Korrektor here: www.youtube.com/watch?v=EhsM...

The LaTeX Korrektor 6/6 - Ten Commandments YouTube video by Andreas Zeller

Series finale! The LaTeX Korrektor 6/6 - Ten Commandments www.youtube.com/shorts/HAodi... #LaTeX #LaTeXKorrektor

Read the LaTeX advice by Diomidis Spinellis (@coolsweng.bsky.social): github.com/dspinellis/l...

All six episodes of the LaTeX Korrektor: www.youtube.com/watch?v=EhsM...

The LaTeX Korrektor 5/6 - Citations YouTube video by Andreas Zeller

Why, oh why does your bibliography have all titles in lowercase? WHY? The LaTeX Korrektor 5/6 - Citations: www.youtube.com/shorts/0nk72... #LaTeX #LaTeXKorrektor

Missed previous episodes? This playlist has them all: www.youtube.com/watch?v=EhsM...

Ah, so it was you who rejected my paper!? 🤔

Thanks! Did you notice the black&white photo in the background?

The LaTeX Korrektor 4/6 - Math Mode YouTube video by Andreas Zeller

Can one reject papers because of bad typography? The LaTeX Korrektor 4/6 - Math Mode: www.youtube.com/shorts/mc8ro... #LaTeX #LaTeXKorrektor

Missed previous episodes? This playlist has them all: www.youtube.com/watch?v=EhsM...