In many organizations, testing fails not due to skill gaps but because there is no structured process.
Testers jump into execution without clarity, requirements remain vague, environments are unstable, and bugs appear late in the cycle. This leads to chaos, missed defects, unexpected delays, and poor-quality releases.

The Software Testing Life Cycle (STLC) solves this by providing a predictable, measurable, and repeatable workflow.
Every tester manual or automation should master it to deliver consistent results.

What is the Software Testing Life Cycle (STLC)?

The Software Testing Life Cycle (STLC) is a step-by-step process followed during software testing to ensure software quality. It defines six structured phases, from analyzing requirements to final test closure, each with specific goals, activities, entry/exit criteria, and deliverables.

STLC vs SDLC

The 6 Phases of STLC:

1. Requirement Analysis

Goal

To understand what needs to be tested and identify testable requirements, ambiguities, and missing information.

Activities

• Analyze SRS, BRD, User Stories, Use Cases.
• Identify functional and non-functional test requirements.
• Perform feasibility analysis for testing.
• Identify test dependencies & risks.
• Clarify doubts with BA/Product Owner.
• Start preparing the Requirement Traceability Matrix (RTM).

Entry Criteria

• Requirements documents are available (BRD/SRS/User Stories).
• Functional & business flows are stable.
• Access to stakeholders for clarifications.

Exit Criteria

• All requirements analyzed and categorized.
• RTM draft completed.
• Requirements understood and signed off by QA lead.

Deliverables

TestingMint Pro Tip:

When requirements are vague, never assume. Document every question in a “Requirement Clarification Log” and get written confirmation. This protects the QA team during sign-off.

2. Test Planning

Goal

To define the overall testing strategy, scope, approach, schedule, estimates, resource allocation, and risk plan.

Activities

• Decide testing types (Functional, API, Regression, Performance, UAT).
• Identify test tools: Selenium, TestNG, Postman, JMeter, etc.
• Estimate effort using WBS or Test Case Count.
• Define entry-exit criteria for execution.
• Plan risk mitigation & test delivery timelines.
• Assign roles and responsibilities.
• Draft and review the Test Plan.

Entry Criteria

• Requirements are analyzed and clear.
• RTM draft is ready.
• High-Level Design available (optional).

Exit Criteria

• Test Plan approved.
• Estimation and schedules finalized.
• Resources assigned.

Deliverables

3. Test Case Development

Goal

To write detailed test cases/test scripts covering all scenarios based on requirements.

Activities

• Create high-quality test cases covering positive, negative, edge cases.
• Prepare test data (valid, invalid, boundary values).
• Automate test cases (if applicable).
• Review test cases internally.
• Update RTM with test case IDs.

Entry Criteria

• Approved Test Plan.
• Clear & stable requirements.
• Test data sources identified.

Exit Criteria

• 100% test cases written and reviewed.
• Test scripts automated (if in scope).
• Test data prepared.
• RTM updated.

Deliverables

4. Test Environment Setup

Goal

To prepare a stable testing environment identical (or close) to production.

Activities

• Set up application build.
• Configure servers, DB, APIs, integrations.
• Deploy automation frameworks.
• Validate the environment with Smoke Testing.
• Arrange access: VPN, credentials, roles.

Entry Criteria

• Test cases ready.
• Environment design shared by DevOps.
• Required tools/licenses procured.

Exit Criteria

• Test environment validated.
• Smoke testing passed.
• All integrations working.

Deliverables

TestingMint Pro Tip:

80% of test delays come from environment issues. Always perform a complete “Environment Readiness Checklist” before starting execution.

5. Test Execution

Goal

To execute test cases, report defects, and ensure the application works as expected.

Activities

• Execute manual test cases.
• Run automated regression scripts.
• Compare actual vs expected results.
• Log defects with severity & priority.
• Retest fixes & perform regression cycles.
• Update test execution status daily.
• Coordinate with Dev/BA for clarifications.

Entry Criteria

• Test environment stable.
• Test cases & data ready.
• Build deployed.

Exit Criteria

• 100% test cases executed.
• All critical defects fixed & verified.
• Regression passed.
• Test summary prepared.

Deliverables

6. Test Cycle Closure

Goal

To evaluate the testing process, document learnings, and officially close the testing cycle.

Activities

• Prepare Test Summary/Closure Report.
• Analyze defect patterns (root cause analysis).
• Conduct QA retrospective meeting.
• Archive test cases, scripts, data.
• Provide sign-off to release management.

Entry Criteria

• All test activities completed.
• All major defects closed or deferred with approval.

Exit Criteria

• Test Closure Report approved.
• Lessons learned documented.
• Test artifacts archived.

Deliverables

TestingMint Pro Tip:

Never skip the “Lessons Learned” document. It is the single most powerful tool for continuous process improvement and avoiding repeated mistakes.

STLC in Action: Testing an E-Commerce “Add to Cart” Button

Let’s apply all 6 phases to a very relatable real-world feature.

1. Requirement Analysis

Questions asked:

• Can a user add 0 items?
• What happens when stock is 0?
• What if the same item is added twice?
• Should the cart show a toast message?
• Should the button be disabled for out-of-stock items?

Deliverables:
RTM, Clarification Log.

2. Test Planning

Decisions:

• Functional testing + negative testing.
• Regression automation in Selenium.
• API validation for Add-to-Cart endpoint.
• Dependencies: Product Catalog API, Inventory Service.

Deliverables:
Test Plan, estimation, schedule.

3. Test Case Development

Sample test cases:

• Add item with quantity 1.
• Add multiple items.
• Add when stock = 0.
• Validate API response for Add-to-Cart.
• Validate UI message after add.

Deliverables:
Test cases + Test data + Automated scripts.

4. Test Environment Setup

Actions:

• Test build deployed (v1.2.5).
• Product DB seeded with test data.
• API gateway configured.
• Smoke testing done.

Deliverables:
Environment readiness checklist, smoke test report.

5. Test Execution

Actions:

• Manual execution of functional cases.
• Automated regression triggered nightly.
• Defects logged:
  • CART-102: Button active when stock = 0.
  • CART-108: API returning HTTP 500.

Deliverables:
Execution report, defect report.

6. Test Cycle Closure

Activities:

• All critical issues fixed and verified.
• Deferred: UI enhancement for cart counter animation.
• Prepared Test Closure Report.
• Lessons learned:
  • Stock API needed early integration.
  • Add-to-Cart service lacked mocks initially.

Deliverables:
Closure Report, Metrics, QA Sign-off.

Conclusion

The Software Testing Life Cycle (STLC) ensures that testing is not done randomly but in a structured, measurable, and repeatable way.
Following these 6 phases leads to better coverage, cleaner releases, fewer production issues, and a mature QA culture.

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