Testing  a  system  with  respect  to  extra-functional  properties  poses  specific  challenges  as  traditional  methods and approaches for testing the system’s functional correctness may not apply. A few examples of such challenges are: fault localization, the need to have appropriate techniques for different types of extra-functional  properties,  the  role  and  impact  of  the  environment  when  testing,  observability  and  testability  issues.  ITEQS  provides  a  well-focused  forum  with  the  goal  of  bringing  together  researchers  and  practitioners to share ideas, identify challenges, propose solutions and techniques, and in general expand the state of the art in testing EFPs and quality characteristics of software systems and services. ITEQS  2018  attracted  8  submissions  (1  withdrawn).  Each  paper  underwent  a  careful  review  and  discussion  process  by  at  least  three  members  of  the  program  committee.  Based  on  the  reviews,  5  papers  were  selected  for  publication  and  presentation  at  the  workshop.  ITEQS  2018  program  includes  keynotes  by Konstantinos Sagonas and Brian Nielsen, who both kindly accepted our invitation. Konstantinos gives a  keynote  on  testing  for  concurrency  bugs  and  Brian  gives  a  keynote  where  he  discusses  how  we  may  achieve a methodology for compositional testing of real-time systems. Finally,  we  would  like  to  thank  our  general  sponsors,  the  publicity  chairs,  the  program  committee,  the  external reviewers, the keynote speakers, the authors and participants. You all contribute to the quality and success of this workshop. Welcome to the workshop! We hope you will enjoy it. xv