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DOI: 10.4230/LIPIcs.ECOOP.2026.13

Automated Inline-Test Generation without Relying on Method-Level Unit Tests

Authors: Pengyue Jiang, Yu Liu, Anna Guo, Milos Gligoric, and Owolabi Legunsen

Published in: LIPIcs, Volume 372, 40th European Conference on Object-Oriented Programming (ECOOP 2026)

Abstract

Inline tests validate individual program statements and expressions, and they detect many seeded faults (i.e., mutants) that unit tests miss in these target statements. ExLi is the only automated inline-test generation technique today; it carves inline tests from method-level unit tests that are written for methods that enclose target statements. Thus, ExLi cannot work for target statements that method-level unit tests do not cover. Also, the quality of ExLi-generated inline tests depends on the quality of method-level unit tests. We propose Smack to generate inline tests without relying on method-level unit tests. Smack is inspired by how inline tests are run: each is extracted with the target statement and run independently. Smack exploits this independence. Smack first extracts each target statement into a new method. Next, Smack applies a unit-test generator to the extracted method, which tends to have simpler control flow than the target statement’s enclosing method and carves inline tests from them. Finally, Smack transplants the resulting inline tests to be right after the target statement in the original enclosing method. We evaluate Smack on the same 957 target statements in 31 open-source projects that ExLi was evaluated on. Smack generates inline tests for 277 of 312 (88.8%) statements that ExLi cannot handle. These inline tests kill 96.7% of 1,815 mutants in these 312 target statements. Therefore, Smack improves on ExLi by extending the reach and fault-detection ability of inline-test generation. Smack also generates inline tests for 609 of 645 (94.4%) target statements that ExLi can handle. Smack-generated inline tests kill 83.1% of 2,844 mutants in these 645 target statements. 147 of these killed mutants survive ExLi-generated inline tests. So, Smack is also complementary to ExLi on target statements that ExLi can handle.

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Pengyue Jiang, Yu Liu, Anna Guo, Milos Gligoric, and Owolabi Legunsen. Automated Inline-Test Generation without Relying on Method-Level Unit Tests. In 40th European Conference on Object-Oriented Programming (ECOOP 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 372, pp. 13:1-13:32, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{jiang_et_al:LIPIcs.ECOOP.2026.13,
  author =	{Jiang, Pengyue and Liu, Yu and Guo, Anna and Gligoric, Milos and Legunsen, Owolabi},
  title =	{{Automated Inline-Test Generation without Relying on Method-Level Unit Tests}},
  booktitle =	{40th European Conference on Object-Oriented Programming (ECOOP 2026)},
  pages =	{13:1--13:32},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-423-9},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{372},
  editor =	{Krebbers, Robbert and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2026.13},
  URN =		{urn:nbn:de:0030-drops-261090},
  doi =		{10.4230/LIPIcs.ECOOP.2026.13},
  annote =	{Keywords: Software testing, inline tests, automated test generation}
}

Document

DOI: 10.4230/LIPIcs.ECOOP.2025.30

In-Memory Object Graph Stores

Authors: Aditya Thimmaiah, Zijian Yi, Joseph Kenis, Christopher J Rossbach, and Milos Gligoric

Published in: LIPIcs, Volume 333, 39th European Conference on Object-Oriented Programming (ECOOP 2025)

Abstract

We present a design and implementation of an in-memory object graph store, dubbed εStore. Our key innovation is a storage model - epsilon store - that equates an object on the heap to a node in a graph store. Thus any object on the heap (without changes) can be a part of one, or multiple, graph stores, and vice versa, any node in a graph store can be accessed like any other object on the heap. Specifically, each node in a graph is an object (i.e., instance of a class), and its properties and its edges are the primitive and reference fields declared in its class, respectively. Necessary classes, which are instantiated to represent nodes, are created dynamically by εStore. εStore uses a subset of the Cypher query language to query the graph store. By design, the result of any query is a table (ResultSet) of references to objects on the heap, which users can manipulate the same way as any other object on the heap in their programs. Moreover, a developer can include (transitively) an arbitrary object to become a part of a graph store. Finally, εStore introduces compile-time rewriting of Cypher queries into imperative code to improve the runtime performance. εStore can be used for a number of tasks including implementing methods for complex in-memory structures, writing complex assertions, or a stripped down version of a graph database that can conveniently be used during testing. We implement εStore in Java and show its application using the aforementioned tasks.

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Aditya Thimmaiah, Zijian Yi, Joseph Kenis, Christopher J Rossbach, and Milos Gligoric. In-Memory Object Graph Stores. In 39th European Conference on Object-Oriented Programming (ECOOP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 333, pp. 30:1-30:30, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{thimmaiah_et_al:LIPIcs.ECOOP.2025.30,
  author =	{Thimmaiah, Aditya and Yi, Zijian and Kenis, Joseph and Rossbach, Christopher J and Gligoric, Milos},
  title =	{{In-Memory Object Graph Stores}},
  booktitle =	{39th European Conference on Object-Oriented Programming (ECOOP 2025)},
  pages =	{30:1--30:30},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-373-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{333},
  editor =	{Aldrich, Jonathan and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2025.30},
  URN =		{urn:nbn:de:0030-drops-233225},
  doi =		{10.4230/LIPIcs.ECOOP.2025.30},
  annote =	{Keywords: Object stores, Graph stores, Cypher}
}

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Automated Inline-Test Generation without Relying on Method-Level Unit Tests

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In-Memory Object Graph Stores

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