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SDLC – Software Development Life Cycle

SDLC defines how software is planned, built, tested, deployed, and maintained. For testers, understanding SDLC is critical to know when to test, what to test, and how to add value at each stage.

Testing is not a separate activity — it is embedded throughout SDLC.

What is SDLC?​

Software Development Life Cycle (SDLC) is a structured process that ensures:

  • Software is built systematically
  • Quality is maintained
  • Risks are reduced
  • Stakeholders are aligned

In simple terms:

SDLC explains how an idea becomes a working software product.

Why Testers Must Understand SDLC​

A tester who understands SDLC can:

  • Participate early (shift-left)
  • Prevent defects instead of just finding them
  • Communicate effectively with developers and managers
  • Align testing with business goals

SDLC Phases (High-Level)​

Typical SDLC consists of the following phases:

  1. Requirement Analysis
  2. Design
  3. Development
  4. Testing
  5. Deployment
  6. Maintenance

Each phase has a tester responsibility.

1️⃣ Requirement Analysis Phase​

What Happens​

  • Business requirements are gathered
  • Functional expectations are defined

Tester’s Role​

  • Review requirements
  • Identify ambiguities
  • Raise questions
  • Start thinking about test scenarios

Early involvement saves cost.

2️⃣ Design Phase​

What Happens​

  • System architecture is created
  • Technical design is prepared

Tester’s Role​

  • Review design documents (awareness)
  • Understand data flow
  • Identify integration points
  • Think about test environment needs

3️⃣ Development Phase​

What Happens​

  • Developers write code
  • Unit testing is performed

Tester’s Role​

  • Clarify requirements
  • Prepare test cases
  • Prepare test data
  • Coordinate with developers

Testing preparation runs in parallel, not after development.

4️⃣ Testing Phase​

What Happens​

  • Test cases are executed
  • Defects are reported
  • Regression testing is performed

Tester’s Role​

  • Execute manual tests
  • Perform functional and regression testing
  • Validate fixes
  • Provide quality sign-off

This is where testers are most visible — but not the only place they add value.

5️⃣ Deployment Phase​

What Happens​

  • Application is released to production or UAT

Tester’s Role​

  • Perform smoke testing
  • Validate critical functionality
  • Support UAT testing
  • Assist release validation

6️⃣ Maintenance Phase​

What Happens​

  • Bugs are fixed
  • Enhancements are added

Tester’s Role​

  • Regression testing
  • Validate bug fixes
  • Ensure no impact on existing features

SDLC Models (Overview)​

Waterfall Model​

  • Sequential phases
  • Testing happens late

Pros:

  • Simple structure

Cons:

  • Late defect discovery
  • High rework cost

Agile Model (Preview)​

  • Iterative development
  • Testing happens continuously

Pros:

  • Early feedback
  • Faster delivery

Agile testing is covered separately in detail.

Common SDLC Misconceptions ❌​

  • Testing is only one phase
  • Testers join after development
  • Quality is tester’s responsibility alone

Reality:

Quality is a shared responsibility across SDLC.

Interview-Ready Questions​

Q: Why is SDLC important for testers?
A: It helps testers plan testing activities and contribute early.

Q: When does testing start in SDLC?
A: From the requirement analysis phase.

Key Takeaways​

  • SDLC defines the software journey
  • Testers play a role in every phase
  • Early testing reduces cost and defects
  • Testing is continuous, not a single step
  • SDLC understanding improves tester effectiveness