Component testing (also known as unit testing or module testing) is a level of testing that focuses on verifying the functionality and quality of individual software components (such as modules, classes, functions, methods, etc.). Component testing mainly tests interfaces and interaction between components, as well as internal logic and data structures of the components. Component testing may be applied using a test-first approach (such as test-driven development or behavior-driven development), where tests are written before the code is implemented. Component testing does not identify defects in modules and classes, as this is a result of component testing, not an objective. Simulators and stubs may be required for component testing, as they can simulate or replace missing or incomplete components or external systems that are needed for testing. Verified References: A Study Guide to the ISTQB® Foundation Level 2018 Syllabus - Springer, page 19.