Chapter 2 – Testing Throughout the SDLC
Bottom-Up Integration – ISTQB Definition
Last Updated: July 12, 2026 · SoftwareTestPilot QA Team
Official ISTQB Definition
An incremental approach to integration testing in which the lowest level components are tested first, then used to facilitate the testing of higher level components.
In simple words
Integrate from the bottom upward, using drivers to call low-level modules.
Exam tip
Requires drivers; contrast with top-down which needs stubs.
Related terms
- Integration TestingAfter units work alone, you plug them together and check the seams — API calls, data hand-offs, contracts.
- Top-Down IntegrationIntegrate from the top downward, using stubs for anything not built yet.
- DriverFake caller code that invokes the module under test when the real caller doesn't exist yet.
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