COTS

• COTS stands for commercial off the shelf software.
• We will not build, but buy a software off the shelf. 
• We spend very little time customizing the software.
• We use CBSE (component based software engineering) to implement COTS.
• Idea to develop software systems by selecting appropriate off the shelf components and then assemble them with a well defined software architecture.
• CBSE has three major functions.
• Developing software from pre-fabricated, reusable parts.
• The ability to use those parts in other applications.
• Easily maintain and customize those parts to produce new functions and features.
• COTS components.
• Independent and replaceable part of a system that fulfills a clear function.
• Works in the context of a well defined architecture.
• A component communicates with other components by its interfaces.
• Developed by different developers, using different languages and different platforms.
• Advantages of COTS.
• Development cost is reduced.
• Development time is reduced.
• Complex systems can be built by reusing pre-existing components.
• Testing effort is reduced.
• Challenges with COTS
• COTS is a black box.
• Lack of functional and technical requirements.
• Level of quality is unknown.
• Unknown development process and methods.
• Compatibility issues.
• Uncertain upgrade schedules and quality.
• Difficulty in regression testing and test automation.
• Inter-operability and integration issues.
• COTS testing techniques
• Black box component testing.
• To understand the behavior of a component, various inputs are executed, and outputs are analyzed.
• To catch all types of errors all possible combination of input values should be executed.
• To make testing feasible test cases are selected randomly from test space.
• System level fault injection.
• A technique for improving the coverage of a test by introducing faults to test code paths.
• Fault, propagate through an observable failure follows a well defined cycle.
• When executed, a fault may cause an error , which is an invalid state within a system boundary.
• An error may cause further errors within the system boundary.
• Each new error acts as a fault.
• When error states are observed at the system boundary they are termed failures.
• This is termed the fault error failure cycle.
• Operational system testing.
• Complements system level fault injection.
• System is operated with random inputs(valid and invalid input)
• Provides more accurate assessment of COTS quality.
• A key operational testing feature is error detection which ensures, correct functional implementation.
• Operational testing allows component interaction.
• Software wrapping.
• Wrapper generally refers to a type of packaging, such as a flat sheet to enclose an object.
• It is a piece of code that one builds to isolate the underlying components from other components of the system.
• A glue component provides the functionality to combine different components.
• Interphase propagation analysis.
• Interface, propagation analysis is used by injecting faults at one component.
• Aggregator design pattern
• Aggregator design pattern can be implemented as an aggregator service which will call more than one micro services based on the needs and collates the response.
• Generate a report form two or more micro services .