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System integration testing

(also SIT)

System integration testing definition

System integration testing (SIT) is a phase in the software testing process that combines individual software modules or components and tests them as a single system to ensure they work together correctly.

See also: software assurance, sandboxing, secure software development lifecycle

Methods of system integration testing

  • Big bang approach. All modules are integrated simultaneously and tested in a single go. This is less structured and can lead to challenges in identifying specific issues.
  • Incremental approach. Modules are integrated and tested one by one.
    • Top-down integration testing. Higher-level modules are tested first, followed by the lower-level modules.
    • Bottom-up integration testing. The opposite of top-down; lower-level modules are integrated and tested before the higher-level ones.
    • Sandwich/hybrid approach. A combination of top-down and bottom-up methods.

Uses of system integration testing

  • To ensure that integrated modules/components work together as intended;
  • To identify interface issues between interacting modules;
  • To validate communication and data transfers among different software components;
  • To ensure a consistent overall behavior of the system.

History of system integration testing

System integration testing emerged in the early stages of the software engineering discipline.

As software systems grew in complexity, so did the necessity for more rigorous testing methods.

  • 1950s and 1960s. Early computing involved relatively simple software, and often relied on manual testing.
  • 1970s. Structured programming and modular design brought the need for integration testing. As software was being developed in modules or components, ensuring these pieces worked together became crucial.
  • 1980s and 1990s. Software applications became even more complex and mission-critical. Methodologies like the Waterfall model focused on distinct testing phases, including SIT.
  • 2000s and beyond. Agile and DevOps brought continuous integration and automated testing, emphasizing real-time system checks.

Today, SIT remains a vital phase in the software development life cycle, especially for large-scale projects.