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TSTL: the template scripting testing language

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Abstract

A test harness, in automated test generation, defines the set of valid tests for a system, as well as their correctness properties. The difficulty of writing test harnesses is a major obstacle to the adoption of automated test generation and model checking. Languages for writing test harnesses are usually tied to a particular tool and unfamiliar to programmers, and often limit expressiveness. Writing test harnesses directly in the language of the software under test (SUT) is a tedious, repetitive, and error-prone task, offers little or no support for test case manipulation and debugging, and produces hard-to-read, hard-to-maintain code. Using existing harness languages or writing directly in the language of the SUT also tends to limit users to one algorithm for test generation, with little ability to explore alternative methods. In this paper, we present TSTL, the template scripting testing language, a domain-specific language (DSL) for writing test harnesses. TSTL compiles harness definitions into an interface for testing, making generic test generation and manipulation tools for all SUTs possible. TSTL includes tools for generating, manipulating, and analyzing test cases, including simple model checkers. This paper motivates TSTL via a large-scale testing effort, directed by an end-user, to find faults in the most widely used geographic information systems tool. This paper emphasizes a new approach to automated testing, where, rather than focus on developing a monolithic tool to extend, the aim is to convert a test harness into a language extension. This approach makes testing not a separate activity to be performed using a tool, but as natural to users of the language of the system under test as is the use of domain-specific libraries such as ArcPy, NumPy, or QIIME, in their domains. TSTL is a language and tool infrastructure, but is also a way to bring testing activities under the control of an existing programming language in a simple, natural way.

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Notes

  1. We also have released a beta version of TSTL for Java [33] to show that testing code in non-scripting languages is also possible.

  2. TSTL does have to scan imports to re-load modules, and also pre-processes function definitions to support pre- and post-conditions.

  3. In fact, TSTL tests are somewhat more general than this already very general and expressive form, in that we do not disallow loops and conditions in actions.

  4. The definition of use is the only distinction between := and normal Python assignment; := is implemented as Python assignment, and appears as such when test cases are printed.

  5. Nondeterministic choice [1, 45,46,47] is both inherent in the notion of a TSTL action, and represented more concretely by the syntactic sugar of the <[...]> notations. Arguably, building the language and semantics around nondeterministic choice to represent a transition system/state space is the core idea of TSTL.

  6. We expect this type to be the same for any TSTL version for any language: a list is the simplest way to express pure sequence, which is the essence of a test.

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Acknowledgements

The authors would like to thank John Regehr, David R. MacIver, Klaus Havelund, our anonymous reviewers, and students in CS362, CS562, and CS569, for discussions related to this work. A portion of this work was funded by NSF Grants CCF-1054786 and CCF-1217824.

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  1. Department of Geography, Pennsylvania State University, State College, USA

    Josie Holmes

  2. School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, USA

    Alex Groce, Jervis Pinto, Pranjal Mittal, Pooria Azimi & Kevin Kellar

  3. Risk Frontiers, Macquarie University, Sydney, Australia

    James O’Brien

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Holmes, J., Groce, A., Pinto, J. et al. TSTL: the template scripting testing language. Int J Softw Tools Technol Transfer 20, 57–78 (2018). https://doi.org/10.1007/s10009-016-0445-y

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