# Automatic Test Improvement with DSpot: a Study with Ten Mature Open-Source Projects

arXiv: https://arxiv.org/abs/1811.08330 · HTML: https://mlsanity.com/paper/1811.08330/

## Key facts

- Cited by 1 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 20 Nov 2018.

## Built on by (most cited first, 1 of 1)

- [Agentic Method for Deterministic Validation of Legacy Code Migration](https://mlsanity.com/paper/2607.28271/) (2026)

## Abstract (arXiv)

In the literature, there is a rather clear segregation between manually written tests by developers and automatically generated ones. In this paper, we explore a third solution: to automatically improve existing test cases written by developers. We present the concept, design, and implementation of a system called dspot, that takes developer-written test cases as input (junit tests in Java) and synthesizes improved versions of them as output. Those test improvements are given back to developers as patches or pull requests, that can be directly integrated in the main branch of the test code base. We have evaluated DSpot in a deep, systematic manner over 40 real-world unit test classes from 10 notable and open-source software projects. We have amplified all test methods from those 40 unit test classes. In 26/40 cases, DSpot is able to automatically improve the test under study, by triggering new behaviors and adding new valuable assertions. Next, for ten projects under consideration, we have proposed a test improvement automatically synthesized by dspot to the lead developers. In total, 13/19 proposed test improvements were accepted by the developers and merged into the main code base. This shows that DSpot is capable of automatically improving unit-tests in real-world, large-scale Java software.