Middleware allows processes running on different machines to communicate across a network and is essential for migrating mainframe applications to client-server architectures and enabling communication between heterogeneous platforms. An effective testing approach includes unit testing by developers, integration testing of program interfaces by developers and independent testers, and system testing of full system requirements and performance by independent testers to ensure acceptance by end users.

1. Middleware is the connectivity software that consists of a set of enabling
services that allow multiple processes running on one or more machines to
interact across a network. Middleware is essential to migrating mainframe
applications to client/server applications and to providing for communication
across heterogeneous platforms.
The testing approach consists of planning and monitoring the software testing
efforts at the various testing levels:
• The unit testing should be performed by the developers. Integration testing
involves testing the program units and their interfaces brought together.
Integration testing should be planned at the design phase and should be
accomplished with an appropriate balance of developers with design knowledge and
independent testers with minimal design biases.
• Systems testing involves in testing of the entire system to verify that system
requirements including specified functions, quality, and performance
characteristics are met. System testing should be planned in the requirement
gathering phase and should be accomplished by independent testers.
• Acceptance testing involves testing the system by actual end users to ensure
that it is ready for delivery and use.