  Context: Continuous integration (CI) is a software engineering technique that
proclaims a set of frequent activities to assure the health of the software
product. Researchers and practitioners mention several benefits related to CI.
However, no systematic study surveys state of the art regarding such benefits
or cons. Objective: This study aims to identify and interpret empirical
evidence regarding how CI impacts software development. Method: Through a
Systematic Literature Review, we search for studies in six digital libraries.
Starting from 479 studies, we select 101 empirical studies that evaluate CI for
any software development activity (e.g., testing). We thoroughly read and
extract information regarding (i) CI environment, (ii) findings related to
effects of CI, and (iii) the employed methodology. We apply a thematic
synthesis to group and summarize the findings. Results: Existing research has
explored the positive effects of CI, such as better cooperation, or negative
effects, such as adding technical and process challenges. From our thematic
synthesis, we identify six themes: development activities, software process,
quality assurance, integration patterns, issues & defects, and build patterns.
Conclusions: Empirical research in CI has been increasing over recent years. We
found that much of the existing research reveals that CI brings positive
effects to the software development phenomena. However, CI may also bring
technical challenges to software development teams. Despite the overall
positive outlook regarding CI, we still find room for improvements in the
existing empirical research that evaluates the effects of CI.
