Integration is defined as the act of enabling the execution of the functionality in a module or application in its true execution environment (TEE). Made that one up, I swear.

The true execution environment is the collective implementation of the module or application and all the other modules and applications that execute along with it as they would be in a production scenario.

• In a lot of cases, it may be impossible to produce an integration environment with all the integrating applications or modules.
• In such a case, clear mention has to be made in the test cases and release documentation, of the missing integration and how development and testing were completed and the pass/fail criteria were determined.
• Stubbing – It is a very good practice to write a proxy or an implementation skeleton of a real integrating application or module in its absence, with the ability to simulate application integration responses as would be in real time.
• A good example is payment / credit card processing. While it may not be possible to use real credit cards and integrate with the credit card processor during unit testing, or even integration testing, it makes sense to build a Proxy layer between the credit card processing API, so that your proxy layer can simulate standard success and failure responses, driven by configuration in the absence of the actual integrating layer.

The main goal of integration is to be able to obtain a build of the entire application with your changes, so that it is possible to test the functionality of the application’s execution in its true production state.