This book constitutes the refereed proceedings of three international workshops held in Rome, Italy, in conjunction with the 15th International Conference on Agile Software Development, XP 2014, in May 2014.The workshops comprised Principles of Large-Scale Agile Development, Refactoring & Testing (RefTest 2014), and Estimations in the 21st Century Software Engineering (EstSE21 2014). The 13 revised full papers presented were carefully reviewed and selected from 28 submissions. In addition, an introduction and a keynote paper are included.

Part: Principles of Large-Scale Agile Development.- Towards Principles of Large-Scale Agile Development: A Summary of the Workshop at XP2014 and a Revised Research Agenda.- Characteristics and Principles of Scaled Agile.- Architecture in Large Scale Agile Development.- Industrial Challenges of Scaling Agile in Mass-Produced Embedded Systems.- Agile in Distress: Architecture to the Rescue.- Conventions for Coordinating Large Agile Projects.- Supporting a Large-Scale Lean and Agile Transformation by Defining Common Values.- A Model for Understanding When Scaling Agile Is Appropriate in Large Organizations.- Control in Software Project Portfolios: A Complex Adaptive Systems Approach.- Part: Refactoring & Testing.- A Measure of the Modularisation of Sequential Software Versions Using Random Graph Theory.- Refactoring Clustering in Java Software Networks.- Are Some Refactorings Attached to Fault-Prone Classes and Others to Fault-Free Classes?.- Capturing Software Evolution and Change through Code Repository Smells.- Considering Polymorphism in Change-Based Test Suite Reduction.- Part: Estimations in the 21st Century Software Engineering.- Effort Estimation in Agile Global Software Development Context.- Early Software Project Estimation the Six Sigma Way.