Where the SDLC covers building software, the Software Testing Life Cycle (STLC) covers the testing effort specifically. It gives testing its own disciplined sequence of phases, each with clear entry and exit criteria.
STLC phases
Requirement analysis
→
Test planning
→
Test design
→
Environment setup
→
Test execution
→
Test closure
What happens in each phase
- Requirement analysis — study what to test and identify testable requirements.
- Test planning — define scope, approach, resources, and schedule.
- Test design — write test cases and prepare test data.
- Environment setup — ready the hardware, software, and data.
- Test execution — run the tests and log defects.
- Test closure — evaluate results, capture lessons, and report.
Entry and exit criteria: each phase should only begin when its inputs are ready and only end when its goals are met. This discipline keeps testing from starting on shaky ground or finishing prematurely.
Conclusion
The STLC gives testing structure and accountability. By following its phases — each with defined entry and exit criteria — teams make the testing effort visible, repeatable, and measurable.