The RET (Requirements Engineering and Testing) workshop series provides a meeting point for researchers and practitioners from the two separate elds of Requirements Engineering (RE) and Testing. The goal is to improve the connection and alignment of these two areas through an exchange of ideas, challenges, practices, experiences and results. The long term aim is to build a community and a body of knowledge within the intersection of RE and Testing, i.e. RET. The 5th workshop was held in colocation with ICSE 2018 in Gothenburg, Sweden. The workshop continued in the same interactive vein as the predecessors. We introduced a new format for the presentations in which the paper authors had the opportunity to interact extensively with the audience. Each author was supported by a member of the organization committee to prepare either an extensive demo, collect more data in form of a questionnaire or perform a hands-on tutorial. We named this new format X-ray session". In order to create an RET knowledge base, this cross-cutting area elicits contributions from both RE and Testing, and from both researchers and practitioners. A range of papers were presented from short positions papers to full research papers that cover connections between the two elds. The workshop attracted 27 participants and the positive feedback on the new format encourages us to organize the workshop the next year again.