We recently proposed inline tests for validating individual program statements; they allow developers to provide test inputs, expected outputs, and test oracles immediately after a target statement. But, existing code can have many target statements. So, automatic generation of inline tests is an important next step towards increasing their adoption. We propose ExLi, the first technique for automatically generating inline tests. ExLi extracts inline tests from unit tests; it first records all variable values at a target statement while executing unit tests. Then, ExLi uses those values as test inputs and test oracles in an initial set of generated inline tests. Target statements that are executed many times could have redundant initial inline tests. So, ExLi uses a novel coverage-then-mutants based reduction process to remove redundant inline tests. We implement ExLi for Java and use it to generate inline tests for 718 target statements in 31 open-source programs. ExLi reduces 17,273 initially generated inline tests to 905 inline tests. The final set of generated inline tests kills up to 25.1% more mutants on target statements than developer written and automatically generated unit tests. That is, ExLi generates inline tests that can improve the fault-detection capability of the test suites from which they are extracted.
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This content will become publicly available on July 17, 2025
ExLi: An Inline-Test Generation Tool for Java
We present ExLi, a tool for automatically generating inline tests, which were recently proposed for statement-level code validation. ExLi is the first tool to support retrofitting inline tests to existing codebases, towards increasing adoption of this type of tests. ExLi first extracts inline tests from unit tests that validate methods that enclose the target statement under test. Then, ExLi uses a coverage-then-mutants based approach to minimize the set of initially generated inline tests, while preserving their fault-detection capability. ExLi works for Java, and we use it to generate inline tests for 645 target statements in 31 open-source projects. ExLi reduces the initially generated 27,415 inline tests to 873. ExLi improves the fault-detection capability of unit test suites from which inline tests are generated: the final set of inline tests kills up to 24.4% more mutants on target statements than developer written and automatically generated unit tests. ExLi is open sourced at https://github.com/EngineeringSoftware/exli and a video demo is available at https://youtu.be/qaEB4qDeds4.
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- Award ID(s):
- 2319473
- PAR ID:
- 10515636
- Publisher / Repository:
- ACM
- Date Published:
- Journal Name:
- The ACM International Conference on the Foundations of Software Engineering (Tool Demonstrations Track)
- Format(s):
- Medium: X
- Location:
- Porto de Galinhas, Brazil, Brazil
- Sponsoring Org:
- National Science Foundation
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