Incremental Integration Testing
Incremental integration testing combines and tests modules one at a time, or in small groups, gradually building up the full system rather than integrating everything at once. Each step tests the newly added module together with what's already been verified, making it much easier to isolate where a failure came from.
Two common patterns: top-down (starting with high-level modules and using stubs to simulate lower-level ones not yet integrated) and bottom-up (starting with low-level modules and using drivers to simulate the higher-level ones that will eventually call them). Both integrate gradually rather than all at once.
The tradeoff versus big bang integration testing is upfront planning cost for much easier debugging later — when a newly integrated module breaks something, the search space for the cause is just that one module and its immediate neighbors, not the entire system.
