  Gamification has been used to motivate and engage participants in software
engineering education and practice activities. There is a significant demand
for empirical studies for the understanding of the impacts and efficacy of
gamification. However, the lack of standard procedures and models for the
evaluation of gamification is a challenge for the design, comparison, and
report of results related to the assessment of gamification approaches and its
effects. The goal of this study is to identify models and strategies for the
evaluation of gamification reported in the literature. To achieve this goal, we
conducted a systematic mapping study to investigate strategies for the
evaluation of gamification in the context of software engineering. We selected
100 primary studies on gamification in software engineering (from 2011 to
2020). We categorized the studies regarding the presence of evaluation
procedures or models for the evaluation of gamification, the purpose of the
evaluation, the criteria used, the type of data, instruments, and procedures
for data analysis. Our results show that 64 studies report procedures for the
evaluation of gamification. However, only three studies actually propose
evaluation models for gamification. We observed that the evaluation of
gamification focuses on two aspects: the evaluation of the gamification
strategy itself, related to the user experience and perceptions; and the
evaluation of the outcomes and effects of gamification on its users and
context. The most recurring criteria for the evaluation are 'engagement',
'motivation', 'satisfaction', and 'performance'. Finally, the evaluation of
gamification requires a mix of subjective and objective inputs, and qualitative
and quantitative data analysis approaches. Depending of the focus of the
evaluation (the strategy or the outcomes), there is a predominance of a type of
data and analysis.
