Understanding the SDLC and STLC as separate concepts is useful, but the real value comes from seeing how they work together. Every SDLC phase produces artefacts that feed into a corresponding STLC phase. When these two life cycles run in parallel, defects are caught earlier, test preparation happens during development rather than after it, and the overall release cycle becomes shorter and more predictable.
How SDLC and STLC Phases Align
The mapping between SDLC and STLC is not one-to-one, but there is a clear correspondence. When the development team is gathering requirements, the testing team should be analysing those same requirements for testability. When developers are designing the system, testers should be designing their test strategy. This parallel execution is what makes “shift-left” testing possible.
# SDLC → STLC mapping: what QA does during each development phase
SDLC_STLC_MAP = [
{
"sdlc_phase": "Requirements Gathering",
"stlc_phase": "Requirements Analysis",
"qa_activities": [
"Review requirements for testability",
"Identify ambiguous or conflicting requirements",
"Begin building the Requirements Traceability Matrix (RTM)",
"Estimate high-level testing effort",
],
"key_artefact": "Requirements Traceability Matrix (RTM)",
},
{
"sdlc_phase": "System Design",
"stlc_phase": "Test Planning",
"qa_activities": [
"Define test strategy (manual vs automated, tools, scope)",
"Identify test environment requirements",
"Plan resource allocation and schedule",
"Create the formal test plan document",
],
"key_artefact": "Test Plan",
},
{
"sdlc_phase": "Implementation (Coding)",
"stlc_phase": "Test Case Design + Environment Setup",
"qa_activities": [
"Write detailed test cases and test scripts",
"Prepare test data sets",
"Configure and validate test environments",
"Conduct test case peer reviews",
],
"key_artefact": "Test Cases + Test Environment",
},
{
"sdlc_phase": "Testing (Integration/System)",
"stlc_phase": "Test Execution",
"qa_activities": [
"Execute test cases and record results",
"Log defects with full reproduction steps",
"Re-test fixed defects and run regression suites",
"Track progress against exit criteria",
],
"key_artefact": "Test Execution Report + Defect Log",
},
{
"sdlc_phase": "Deployment + Maintenance",
"stlc_phase": "Test Closure",
"qa_activities": [
"Conduct smoke and sanity testing post-deployment",
"Generate test summary report with metrics",
"Hold lessons-learned retrospective",
"Archive artefacts for future regression baselines",
],
"key_artefact": "Test Summary Report",
},
]
print(f"{'SDLC Phase':<30} {'STLC Phase':<35} {'Key Artefact'}")
print("=" * 95)
for row in SDLC_STLC_MAP:
print(f"{row['sdlc_phase']:<30} {row['stlc_phase']:<35} {row['key_artefact']}")
Common Mistakes
Mistake 1 — Treating SDLC and STLC as completely independent processes
❌ Wrong: "The developers follow the SDLC and testers follow the STLC — they are separate tracks that do not interact until the build is thrown over the wall."
✅ Correct: "The SDLC and STLC are parallel, interconnected processes. Each SDLC phase produces artefacts that feed into the corresponding STLC phase, enabling continuous quality checks rather than a single late testing gate."
Mistake 2 — Not starting test environment setup until after test cases are written
❌ Wrong: Waiting until all test cases are approved before requesting a test environment, then losing days to setup issues.
✅ Correct: Beginning environment setup during the Implementation phase so that when test cases are ready, the environment is already validated and the team can start execution immediately.