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The Behaviour Specification Handbook
Background
What Is A Software Component?
A software component is a logical grouping of functionality that is represented as an application, sub-system, service, micro-service, library, module, or any sort of implementation of part of an architectural layer. The granularity and boundaries between software components really depends on what makes logical sense. As a general guideline, a software component typically is larger than one class or module — although this guideline may not apply in the case of micro-services.
For example, a software component could be the functionality that provides the User Interface for a screen, or it could be the functionality of a back-end service operation. A software component also could be a specific part of a data access layer or repository.
Teams should carefully consider the design of their software components, as these choices affect later stages of the software development lifecycle. If a team ever struggles with maintaining a well structured Testing Pyramid, consider reviewing the boundaries of the software components. Splitting a large component into many, each with less responsibilities, could open the door to simplified Behaviour Specifications, a better Testing Pyramid, easier comprehension of functionality, and a lower total cost of ownership.