Today, the concept of approximation in computing is becoming more and more a "hot topic" to investigate how computing systems can be more energyefficient, faster, and less complex. Intuitively, instead of performing exact computations and, consequently, requiring a high amount of resources, Approximate Computing aims at selectively relaxing the specifications, trading accuracy off for efficiency. While Approximate Computing allows many improvements when looking at systems' performance, energy efficiency and complexity, it poses significant challenges regarding the design, the verification, the test and the in-field reliability of Approximate Digital Integrated Circuits. This chapter covers these aspects, leveraging the authors' experience in the field to present state-of-the-art solutions to apply during the different development phases of an Approximate Computing system.