License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.ECOOP.2020.13
URN: urn:nbn:de:0030-drops-131700
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MacIver, David R. ; Donaldson, Alastair F.

Test-Case Reduction via Test-Case Generation: Insights from the Hypothesis Reducer (Tool Insights Paper)

LIPIcs-ECOOP-2020-13.pdf (0.5 MB)


We describe internal test-case reduction, the method of test-case reduction employed by Hypothesis, a widely-used property-based testing library for Python. The key idea of internal test-case reduction is that instead of applying test-case reduction externally to generated test cases, we apply it internally, to the sequence of random choices made during generation, so that a test case is reduced by continually re-generating smaller and simpler test cases that continue to trigger some property of interest (e.g. a bug in the system under test). This allows for fully generic test-case reduction without any user intervention and without the need to write a specific test-case reducer for a particular application domain. It also significantly mitigates the impact of the test-case validity problem, by ensuring that any reduced test case is one that could in principle have been generated. We describe the rationale behind this approach, explain its implementation in Hypothesis, and present an extensive evaluation comparing its effectiveness with that of several other test-case reducers, including C-Reduce and delta debugging, on applications including Python auto-formatting, C compilers, and the SymPy symbolic math library. Our hope is that these insights into the reduction mechanism employed by Hypothesis will be useful to researchers interested in randomized testing and test-case reduction, as the crux of the approach is fully generic and should be applicable to any random generator of test cases.

BibTeX - Entry

  author =	{David R. MacIver and Alastair F. Donaldson},
  title =	{{Test-Case Reduction via Test-Case Generation: Insights from the Hypothesis Reducer (Tool Insights Paper)}},
  booktitle =	{34th European Conference on Object-Oriented Programming (ECOOP 2020)},
  pages =	{13:1--13:27},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-154-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{166},
  editor =	{Robert Hirschfeld and Tobias Pape},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{},
  URN =		{urn:nbn:de:0030-drops-131700},
  doi =		{10.4230/LIPIcs.ECOOP.2020.13},
  annote =	{Keywords: Software testing, test-case reduction}

Keywords: Software testing, test-case reduction
Collection: 34th European Conference on Object-Oriented Programming (ECOOP 2020)
Issue Date: 2020
Date of publication: 06.11.2020

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