STLC – Software Testing Life Cycle
STLC explains how testing activities are planned, executed, and closed. While SDLC explains how software is built, STLC explains how testing is done in a structured and controlled way.
For testers, STLC represents the day-to-day workflow in real projects.
What is STLC?
Software Testing Life Cycle (STLC) is a sequence of activities performed by the testing team to:
- Ensure quality
- Reduce risk
- Deliver a stable product
In simple words:
STLC explains how testers work from requirement to release.
Why STLC is Important
STLC helps testers:
- Plan testing properly
- Avoid ad-hoc testing
- Track progress
- Control quality
- Provide clear sign-off
Projects without STLC usually suffer from:
- Missed test coverage
- Poor reporting
- Last-minute chaos
STLC Phases (Complete Flow)
- Requirement Analysis
- Test Planning
- Test Case Design
- Test Environment Setup
- Test Execution
- Test Closure
Each phase has entry and exit criteria.
1️⃣ Requirement Analysis (STLC)
Activities
- Analyze functional requirements
- Identify testable requirements
- Identify test scenarios
- Clarify ambiguities
Deliverables
- Test scenarios
- Requirement questions
- Initial test strategy inputs
2️⃣ Test Planning
Activities
- Define test scope
- Identify test types
- Estimate effort
- Identify risks
- Decide test approach
Deliverables
- Test plan document
- Test schedule
- Resource allocation
Tester note:
Good test planning prevents last-minute surprises.
3️⃣ Test Case Design
Activities
- Write test cases
- Prepare test data
- Review test cases
Deliverables
- Test cases
- Test data
- Review comments
This phase heavily depends on requirement clarity.
4️⃣ Test Environment Setup
Activities
- Verify test environment readiness
- Validate access
- Check test data availability
Environment Examples
- QA
- UAT
- Staging
Without a stable environment, testing cannot proceed.
5️⃣ Test Execution
Activities
- Execute test cases
- Mark pass/fail/block
- Log defects
- Perform regression testing
Deliverables
- Execution results
- Defect reports
- Daily status reports
6️⃣ Test Closure
Activities
- Evaluate test completion
- Analyze defects
- Prepare test summary report
- Get sign-off
Deliverables
- Test closure report
- Lessons learned
This phase provides confidence to release.
Entry & Exit Criteria (Important)
Entry Criteria
- Requirements approved
- Environment ready
- Test cases reviewed
Exit Criteria
- Critical defects closed
- Test coverage achieved
- Stakeholder sign-off
STLC vs SDLC
| Aspect | SDLC | STLC |
|---|---|---|
| Focus | Development | Testing |
| Owner | Dev + Mgmt | QA |
| Scope | End-to-end | Test activities |
| Nature | Product-centric | Quality-centric |
Common STLC Mistakes ❌
- Skipping test planning
- Rushing test case design
- Ignoring exit criteria
- Poor test closure
Interview-Ready Questions
Q: What is STLC?
A: A structured approach to plan, execute, and close testing activities.
Q: Why is STLC important?
A: It ensures quality, traceability, and controlled testing.
Key Takeaways
- STLC defines tester workflow
- Each phase has clear deliverables
- Entry & exit criteria control quality
- Strong STLC leads to predictable testing
- Essential for real projects and interviews