This book contributes to the growing field of foreign language teaching and testing by shedding light on mediation between languages. Stathopoulou offers an empirically-grounded definition of mediation as a form of translanguaging and offers tools and methods for further research in multilingual testing. The book explores what cross-language mediation entails, what processes and strategies are involved, and the challenges often faced by mediators. As well as stressing the importance of administering tests which favour cross-language mediation practices, the author encourages the implementation of language programmes which promote the mingling-of-languages idea and target the development of language learners' effective translanguaging practices. Researchers studying translanguaging, multilingualism, multilingual testing and the use of mother tongue in the foreign language classroom will all find this book of interest.