1. SDLC (Software Development Life Cycle)
Definition
The Software Development Life Cycle (SDLC) is a structured process used to develop software. It defines the steps to plan, create, test, and deploy software efficiently and with quality.
Key Goal: Deliver high-quality software that meets user requirements, on time and within budget.
Phases of SDLC
| Phase | Description |
|---|---|
| 1. Requirement Gathering & Analysis | Collect and analyze business/user requirements. Create requirement specification document (SRS). |
| 2. Feasibility Study | Check technical, operational, and economic feasibility. Decide if project is viable. |
| 3. Design | Create software architecture and design documents. Includes UI/UX design, database design, and system design. |
| 4. Development / Implementation | Write code based on design documents. Usually done in iterations for Agile methodology. |
| 5. Testing | Verify the software functionality, performance, and security. Identify and fix bugs. |
| 6. Deployment | Release software to production or client environment. |
| 7. Maintenance | Bug fixing, updates, and adding new features based on user feedback. |
SDLC Models
- Waterfall Model – Sequential, one phase at a time.
- Agile Model – Iterative, incremental development with continuous feedback.
- V-Model – Testing activities aligned with development phases.
- Spiral Model – Risk-driven iterative approach.
- Iterative Model – Develop software in repeated cycles.
Key Points About SDLC
- Focuses on development process.
- Ensures proper planning, design, implementation, and maintenance.
- Helps reduce cost, risk, and time.
2. STLC (Software Testing Life Cycle)
Definition
The Software Testing Life Cycle (STLC) is a sequence of steps performed to ensure quality of the software. It focuses specifically on testing activities in a systematic way.
Key Goal: Detect defects early and ensure the software meets requirements and quality standards.
Phases of STLC
| Phase | Description |
|---|---|
| 1. Requirement Analysis | Understand functional and non-functional requirements to identify testable features. |
| 2. Test Planning | Define scope, strategy, resources, schedule, and tools for testing. |
| 3. Test Case Design / Test Scenario Creation | Create detailed test cases, scenarios, and test data. |
| 4. Test Environment Setup | Prepare hardware, software, network, and database needed for testing. |
| 5. Test Execution | Run test cases and report defects if actual results differ from expected results. |
| 6. Defect Reporting & Tracking | Log defects in a tool (like JIRA), track status, retest after fixes. |
| 7. Test Closure | Prepare test summary reports, evaluate quality, and document lessons learned. |
Key Points About STLC
- Focuses only on testing activities.
- Ensures quality, reliability, and correctness of software.
- Helps in finding defects early, reducing cost of fixes.
3. Differences Between SDLC and STLC
| Feature | SDLC | STLC |
|---|---|---|
| Full Form | Software Development Life Cycle | Software Testing Life Cycle |
| Focus | Software development process | Software testing process |
| Purpose | Deliver functional software | Ensure software quality |
| Phases Covered | Requirement, Design, Coding, Testing, Deployment, Maintenance | Requirement Analysis, Test Planning, Test Design, Execution, Closure |
| Performed By | Developers, Designers, Business Analysts | Testers / QA team |
| Outcome | Working software | Tested and defect-free software |
| Start Point | Requirement gathering | After requirement analysis |
| End Point | Maintenance of software | Test closure / sign-off |
4. How SDLC and STLC Work Together
- SDLC includes development + testing, while STLC is only about testing.
- Testing starts in parallel with SDLC phases (especially in V-Model or Agile).
- Good collaboration between SDLC & STLC ensures high-quality software delivered on time.
5. Summary
- SDLC: End-to-end software development process.
- STLC: Systematic testing process within SDLC.
- Both ensure quality, efficiency, and defect-free software.
- Testers and developers work together for successful software delivery.