The C-Test as a tool for assessing language competence has been in existence for nearly 40 years, having been designed by Professors Klein-Braley and Raatz for implementation in German and English. Much research has been conducted over the ensuing years, particularly in regards to reliability and construct validity, for which it is reported to perform reliably and in multiple languages. The author engaged in C-Test research in 1995 focusing on concurrent, predictive and face validity. Through this research, the author developed an appreciation for the C-Test assessment process particularly with the multiple cognitive and linguistic test-taking strategies required. When digital technologies became accessible, versatile and societally integrated, the author believed the C-Test would function well in this environment. This conviction prompted a series of investigations into the development and assessment of a digital C-Test design to be utilised in multiple linguistic settings. This paper describes the protracted design process, concluding with the publication of mobile apps.