Context. Due to the uniqueness of software projects there is no single Agile development approach that ideally fits all project contexts. Each software project is unique, whether in its subject area, development team, or project size. Because of this, adapting Agile practices according to project circumstances is a must. There has been a number of literature published discussing Agile practices adaptation topic. However, it is still unclear how to adapt Agile practices. Therefore, researchers as well as practitioners need to find out the knowledge of how the Agile practices adaptation should be applied in software development project. Objectives. In this study we investigate how companies adapt their software development practices when they claim they use Agile software development. Knowledge about this can assist Agile software practitioners to apply Agile practices adaptation in their own context and obtain the most benefit out of Agile software development. Methods. We used systematic literature review using guidelines from Kitchenham and survey in this research study. In the systematic review, a number of relevant article sources were used including peer-reviewed papers and grey literature. Peer-reviewed papers were searched from several electronic databases. Grey literature was also included, which covered books, theses and dissertations, white papers and website/blog articles. The survey was executed using a web based survey tool which invited Agile practitioners from a broad range of industries. In total there are 79 selected literature reviewed in the systematic review comprising 63 peer-reviewed papers and 16 grey literature. Data extraction results were categorized into used and unused Agile practices, adapted practices, additional practices, importance of practices, adaptation challenges and solutions recommended by Agile practitioners. Furthermore, an online survey was conducted with a total of 700 respondents of which 468 responses completed the survey. Only the completed and valid responses were considered in the results analysis. We classify the survey results into several categories: Agile practices usage scale, importance of practices, details of adaptation, Agile practices instruction/guidelines, and Agile practitioners‟ adherence to the instruction/guidelines. Results. Our systematic review shows that some companies used Agile practices in literature with various degrees of adaptation. Several companies creatively used a hybrid of Agile practices from various Agile approaches. In addition, we found that most of the Agile practices, especially in the XP approach, have to be adapted appropriately according to company software development context. On the other hand, survey results show that most of the Scrum practitioners apply Scrum practices without adaptation. Regarding importance of practices, unit testing/Test-Driven Development and continuous integration are identified by XP practitioners as the most important practices. For Scrum practitioners, the most important practices are product/feature backlog and Sprint. Conclusions. Many reasons are discovered why adaptation of Agile practice is necessary e.g. to suit with software development context or for effectiveness reason. Therefore, better support from management and developers is needed to facilitate Agile practices adaptation. Different degrees of adaptation also depend on the type of implemented Agile approach. XP as a technical approach requires more adaptation when compared to project management approach such as Scrum. Findings regarding respondents‟ adherence to the Agile instruction/guidelines indicate the need to improve quality of Agile instructions/guidelines and Agile leadership and enforce the implementation of instructions/guidelines as well.

This thesis investigates how companies adapt their software development practices when they claim they use Agile software development based on the systematic review on Agile literature and an online survey. The derived knowledge from this thesis can assist Agile software practitioners to adapt Agile practices in their own context and maximize the benefit of Agile software development.