A Guide on Types of Integration Testing
Tags: integration, testing
Published: 2024-05-01 07:51:59

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Integration testing is an important part of testing software. It involves testing individual software modules as a group to verify that they interact correctly. The purpose of integration testing is to identify defects and inconsistencies between integrated modules. There are different types of integration testing, each with its own approach and use cases. In this blog, we will cover all the major types of integration testing.

**Unit Testing**

Unit test basically covers testing the components of the code either function by itself or class by itself. It is run while the code is being written to ensure that the code meets the requirements on functionality, reliability, and performance.  Unit testing establishes confidence that the foundational building blocks of an application work as intended before integration testing begins. It builds a solid base on which higher levels of testing can build.

**API Testing**

API (Application Programming Interface) testing is designed to test application interfaces and validate that communication and data exchanges happen correctly. API testing ensures endpoints and interface calls operate as expected by sending API calls and examining the responses. This is critical for applications that connect with external services or expose interfaces to other applications. Focused API testing before broader integration allows interface issues to be addressed early.

**Interface Testing**

Related to API testing, interface testing targets the connections between systems and verifies the touchpoints operate correctly. Rather than only looking at data structures, it validates that system handoffs work across the software interfaces. Interface testing suites should include positive path scenarios, negative cases, erroneous data, and security checks at system boundaries.

**Regression Testing**

Regression testing means re-running integration test suites that have already been executed on an application after changes, upgrades, or patches have been made. It checks for unexpected changes or regressions in functionality due to code alterations. By systematically retesting integrated components, unintended effects of even small changes can be caught. Disciplined regression testing greatly increases stability across software revisions.

**Smoke and Sanity Testing**  
 
Smoke tests form a preliminary set of broad tests to gauge system integrity at a basic level. Sanity testing takes this quick validation a bit deeper with more specific test cases while still not getting into detailed testing. Together these test types give Build Verification Tests that check for major issues and establish confidence in fundamental functionality, integration, and performance.

**End-to-end Testing**

End-to-end (E2E) testing involves comprehensive testing of an application in environments and scenarios modeled on real-world use. All components, interfaces, frontend, APIs, database, authentication systems, integrations, user flows, and experiences are tested together as user stories are driven through the entire product. The system as a whole is validated, with a focus on both functionality and design. End-to-end testing is the closest form of testing mimicking real usage.

**Conclusion**

There is a wide variety of integration testing types, each serving an important purpose. Unit tests establish building blocks, API tests ensure communication over interfaces, smoke, and sanity tests build confidence in deployed applications, regression tests reduce unexpected changes on updates, and end-to-end testing validates the full product experience. A quality integration testing strategy will incorporate different methods at multiple test levels.

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