The well-known testing framework JUnit has come a long way since its inception in 1995. On September 10, 2017, an important milestone in the project life cycle took place, i.e. the release of JUnit 5.0.0. Before going deep into the details of JUnit 5, it is worth reviewing the status quo of software testing, in order to understand from where we have come, and where we are going. To that aim, this chapter provides a high-level review of the background of software quality, software testing, and testing for Java. Concretely, the chapter is composed of three sections:

• Software quality: The first section reviews the status quo in quality engineering: Quality assurance, ISO/IEC-2500, Verification & Validation (V&V), and software defects (bugs).
• Software testing: This is the most commonly performed activity to guarantee software quality and reduce the number of software defects. This section provides a theoretical background of software testing levels (unit, integration, system, and acceptance), methods (black-box, white-box, and non-functional),  automated and manual software testing.
• Testing frameworks for the Java Virtual Machine (JVM): This section provides a summary of the main features of the legacy versions of the JUnit framework (that is, versions 3 and 4). Finally, a brief description of alternative testing frameworks and enhancers to JUnit is depicted.