What is STLC in Software Testing? The 6 Phases Explained (2026)
STLC — the Software Testing Life Cycle — is the 6-phase process from requirements analysis to test closure. Learn each phase, entry/exit criteria, and how STLC differs from SDLC.
Last updated: July 11, 2026 · 9 min read
The Software Testing Life Cycle (STLC) is the structured process QA teams follow across every release. This guide walks through all six phases with entry and exit criteria, and shows how STLC fits inside the broader SDLC. Complements our Manual Testing Complete Guide.
What is STLC?
STLC is a systematic, phase-based approach to testing software. Each phase has defined entry and exit criteria, deliverables, and owners. Following STLC keeps testing predictable, traceable, and audit-ready — which is why regulated industries (fintech, healthtech, aviation) rely on it.
The 6 phases of STLC
- Requirement Analysis — QA reads BRD/PRD, identifies testable and non-testable requirements, raises ambiguity queries.
- Test Planning — Test Lead writes the test plan: scope, approach, resources, schedule, risks.
- Test Case Design — QAs write test cases and prepare test data. Traceability matrix links each requirement to test cases.
- Test Environment Setup — DevOps/QA provisions servers, test data, integrations. Smoke test confirms environment is testable.
- Test Execution — Tests are run (manual + automated). Defects logged, retested, and closed. Daily status reports.
- Test Closure — Metrics compiled (coverage, defect density, escape rate), retrospective run, artifacts archived.
Entry & exit criteria per phase
| Phase | Entry Criteria | Exit Criteria |
|---|---|---|
| Requirement Analysis | BRD/PRD available | Testable requirements signed off |
| Test Planning | Requirements finalized | Approved test plan |
| Test Case Design | Test plan signed off | Reviewed test cases + traceability matrix |
| Environment Setup | Hardware/software list ready | Smoke test passes |
| Test Execution | Test cases + env ready | All planned tests executed, criticals fixed |
| Test Closure | Testing complete | Test summary + lessons-learned published |
STLC vs SDLC
SDLC is the entire software delivery process — requirements, design, build, test, deploy, maintain. STLC is the testing slice that runs inside SDLC. In agile teams, STLC phases compress and overlap: analysis and case design happen inside a two-week sprint, closure at sprint end.
STLC in Agile and DevOps
- Requirement analysis happens in the Three Amigos meeting (PM + Dev + QA).
- Test planning becomes a lightweight test strategy per sprint or per epic.
- Case design uses BDD/Gherkin (Cucumber docs).
- Execution shifts left — unit tests on every commit, regression nightly.
- Closure becomes continuous — dashboards, not documents.
Key STLC deliverables
- Requirement Traceability Matrix (RTM)
- Test Plan document
- Test cases and test data
- Test execution report
- Defect report
- Test summary / closure report
Continue your learning
Frequently asked questions
Who owns each STLC phase?
Test Lead owns planning and closure. Individual QAs own case design, execution, and defect logging. DevOps/Test Environment Manager owns environment setup.
How long does STLC take?
Waterfall teams may spend weeks per phase. Agile teams compress the full cycle into a two-week sprint by parallelizing analysis, design, and execution.
What's the difference between STLC and V-model?
V-model is a development model that pairs each dev phase with a test phase. STLC is a pure testing process — it lives inside the right side of the V.
Is STLC still relevant in DevOps?
Yes, but reshaped. Phases become continuous flows — planning per sprint, execution per commit, closure via dashboards — rather than sequential gates.
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