Universal Dependencies - English - GUM

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Design of Mutation Operators for Testing Geographic Information Systems

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Suilen H. Alvarado Laboratorio de Bases de Datos Campus de Elviña, Centro de investigación CITIC, Universidade da Coruña, 15071 A Coruña, Spain; s.hernandez@udc.es

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Presented at the 2nd XoveTIC Congress, A Coruña, Spain, 5–6 September 2019.

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Abstract:

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In this article, we propose the definition of specific mutation operators for testing Geographic Information Systems.

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We describe the process for applying the operators and generating mutants, and present a case study where these mutation operators are applied to two real-world applications.

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Keywords: mutation operators; geographic information systems; mutation testing

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1. Introduction

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Mutation-based testing [1] is a test technique that involves artificially introducing errors into a System Under Test (SUT).

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A mutant is a copy of the system in which a change has been done that, in most cases, will lead to a behaviour different than expected.

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The different mutants are generated automatically by the application of mutation operators.

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In the state of the art, we have found mutation operators, both general purpose and specific to different technologies, languages and paradigms [2–9].

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However, these operators are not adequate when trying to test software features associated with specific domains.

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In this article, we propose mutation operators specific to the domain of Geographic Information Systems (GIS) applications.

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These operators reproduce programming errors that are litely to occur during the development of this type of applications.

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In addition, we present the implementation of these operators and as proof of concept we apply these operators to two real-world GIS applications and we generate the mutants.

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2. Mutation Operators for GIS

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As a previous step to designing the mutation operators, we analyzed the main technologies used specifically in the development of GIS, and we identified typical errors a programmer can introduce during the development.

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These errors were formalized into mutation operators.

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In order to apply these operators to a SUT, we rely on Java reflection and aspect-oriented programming.

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Reflection allows us to obtain the list of classes and methods of the SUT, so the user can decide the methods to wish the operators will be applied.

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Later, we capture information about the methods of the SUT to be mutated, together with the information of the mutation operators that were already defined.

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From these data, we generate the mutation operator, in the form of on aspect, which will then be possible to interweave with the SUT which generates a mutant of the SUT.

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Next, we describe the definition of two operators and two cases of application on real-world GIS applications.

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ChangeCoordSys Operator (Listing 1):

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It exchanges the coordinate system of a geometry, so it does not match the coordinate system that is being used in the user interface.

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It simulates the error of not checking that the coordinate system is correct.

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The error is introduced by directly modifying the coordinate system of geometry when recovering the wrapping of the figure.

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Listing 1: A simplified definition of the ChangeCoordSys Operator.

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This operator was applied to a mobile technology GIS application.

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This application allows registering places of interest for the user.

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These areas of interest are called Geofences.

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A Geofence is determined by a geographical location expressed in terms of latitude, longitude, and a radius around that location.

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By creating a Geofence with an erroneous location from its central location, the device will receive incorrect location notifications.

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As a result, the user will see in the application’s map viewer the Geofences drawn in erroneous zones (Figure 1).

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Figure 1. Original and mutant application.

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BooleanPolygonConstraint Operator (Listing 2):

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It introduces errors in the processing of geometries, manipulating the result of the operations that carry out the verification of different topological restrictions between geometries, such as intersects, covers or overlap.

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Listing 2: A simplified definition of the BooleanPolygonConstraint Operator.

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To test this operator it was applied to a land reparcelling system.

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The objective of the land reparcelling is to reunify the lands of an owner to facilitate their exploitation.

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In this application, the result of the operation between two polygons has been affected.

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This error causes the incorrect display of the resulting geometry that should be drawn in the user interface after the operation applied to the two initial geometries (Figure 2).

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Figure 2. Original and mutant application.

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3. Conclusions

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In existing proposals, we can find both generic and specific mutation operators.

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However, these are not adequate to cover errors in particular domains.

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We have defined new operators specific to the GIS domain and a way to apply them to a SUT.

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In addition, we have tested the operators defined in two GIS applications.

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As future work, we intend to extend this approach to other domains, as well as to use the developed operators for the automatic improvement of sets of test cases.