Prompt Debloating for LLM-based Test Generation with Graph-Augmented Retrieval

Abstract

The use of Large Language Models (LLMs) for automated test generation offers
promising results but remains constrained by issues like hallucinations and
prompt size limitations. This thesis investigates the integration of a graph-based
Retrieval Augmented Generation (RAG) technique to enhance test generation
within TestSpark, an IntelliJ IDEA plugin. We introduce GRACE-TG (Graph-
Retrieved Augmented Contextual Enhancement for Test Generation), which constructs
a graph of code entities using the Program Structure Interface (PSI) and
rank nodes via a Personalized Weighted PageRank algorithm. This enables a
precise selection of relevant context for LLMs while significantly reducing input
size. Evaluation across 147 real-world Java bugs demonstrates that GRACE-TG
reduces prompt sizes by over 97% compared to the current version of TestSpark,
with equivalent or improved test coverage. These results suggest that graph-based
retrieval can be a good candidate to improve test generation with LLMs.

Date of Award	1 Sept 2025
Original language	English
Awarding Institution	University of Namur
Supervisor	Xavier Devroey (Jury)