Test smells are, analogously to code smells, defined as the characteristics exhibited by poorly designed unit tests. Their negative impact on test effectiveness, understanding, and maintenance has been demonstrated by several empirical studies.However, the scope of these studies has been limited mostly to JAVA in combination with the JUNIT testing framework. Results for other language and framework combinations are -despite their prevalence in practice-few and far between, which might skew our understanding of test smells. The combination of SCALA and SCALATEST, for instance, offers more comprehensive means for defining and reusing test fixtures, thereby possibly reducing the diffusion and perception of fixture-related test smells.This paper therefore reports on two empirical studies conducted for this combination. In the first study, we analyse the tests of 164 open-source SCALA projects hosted on GITHUB for the diffusion of test smells. This required the transposition of their original definition to this new context, and the implementation of a tool (SOCRATES) for their automated detection. In the second study, we assess the perception by and the ability of 14 SCALA developers to identify test smells. For this context, our results show (i) that test smells have a low diffusion across test classes, (ii) that the most frequently occurring test smells are LAZY TEST, EAGER TEST, and ASSERTION ROULETTE, and (iii) that many developers were able to perceive but not to identify the smells.

Among distributed applications, the actor model is increasingly prevalent. This programming model organises applications into fully-isolated processes that communicate through asynchronous messaging. Supported by frameworks such as Akka and Orleans, it is believed to facilitate realising responsive, elastic and resilient distributed applications.While these frameworks do provide abstractions for implementing resilience, it remains up to developers to use them correctly and to test that their implementation recovers from anticipated failures. As manually exploring the reaction to every possible failure scenario is infeasible, there is a need for automated means of testing the resilience of a distributed application.We present the first automated approach to testing the resilience of actor programs. Our approach perturbs the execution of existing test cases and leverages delta debugging to explore all failure scenarios more efficiently. Moreover, we present a further optimisation that uses causality to prune away redundant perturbations and speed up the exploration. However, its effectiveness is sensitive to the program's organisation and the actual location of the fault. Our experimental evaluation shows that our approach can speed up resilience testing by four times compared to random exploration. CCS CONCEPTS• Computer systems organization → Reliability; Fault-tolerant network topologies; • Software and its engineering → Software testing and debugging.

Test smells are indications of poorly designed unit tests. Previous studies have demonstrated their negative impact on test understanding and maintenance. Moreover, surveys show that developers are not able to identify test smells, hindering optimal software quality. Automated tools can aid developers to handle these issues and detect test smells in the early stage of software development. However, few tools are publicly available and all of them target JUnitthe most popular testing framework in Java. To overcome these limitations, we propose SoCRATES. This fully automated tool is able to identify six test smells in ScalaTest which is the most prevalent testing framework in Scala. An empirical investigation on 164 Scala projects shows that our tool is able to reach a high precision without sacrificing recall. Moreover, the results show that Scala projects have a lower diffusion than Java projects. We make SoCRATES publicly available as an IntelliJ IDEA plugin, as well as an open-source project in order to facilitate the detection of test smells.

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