The Software Testing Life Cycle, or STLC, is a structured process that describes the main testing activities performed during a project.
In simple words, STLC helps answer:
STLC helps testing stay organized and systematic.
1. Requirement Analysis 2. Test Planning 3. Test Case Design 4. Test Execution 5. Test Closure
Let us look at each phase.
Requirement analysis is the phase where testers study the requirements and try to understand:
what the system should do • what needs to be tested • what may be risky • whether the requirements are clear, complete, and testable
This is one of the earliest and most important testing activities.
If the requirements are unclear, incomplete, or contradictory, testing becomes difficult.
For example:
A requirement says: “The user should receive confirmation quickly after payment.”
This is not very clear.
A tester may ask: • What does “quickly” mean? • Is it 1 second? 5 seconds? 30 seconds? • What kind of confirmation, email, screen message, SMS?
This is useful because testing starts with understanding.
Testers may: • review requirements and user stories • ask questions • identify missing details • identify risks • identify test conditions • check whether the requirements are testable
Requirement: The user can reset the password by email.
Possible tester questions: • What happens if the email does not exist? • How long is the reset link valid? • Can the link be used more than once? • What message is shown after success or failure?
These questions improve quality before testing even starts.
Test planning is the phase where the team decides how testing will be organized.
It answers questions like: • what will be tested • what will not be tested • which test types will be used • who will do the testing • when testing will happen • what tools, environments, and data are needed • what risks exist
Without planning, testing easily becomes chaotic.
A good test plan helps the team: • stay aligned • use time better • focus on priorities • manage risks • communicate clearly
Imagine a team is releasing a food delivery app update.
Without planning: • one tester focuses on profile settings • another tests restaurant search • nobody tests checkout and payment
That is dangerous, because payment is business-critical.
With planning: • critical flows are identified first • responsibilities are clearer • risk areas get more attention
Test case design means preparing the tests that will later be executed.
This may include: • test cases • test scenarios • checklists • test data • expected results
Good test design helps testers:
cover important functionality test systematically
reduce missed scenarios
make execution more efficient
Feature: Login
Possible test cases: • login with valid username and valid password • login with valid username and invalid password • login with empty fields • login with locked account • login with password shorter than allowed • login after several failed attempts
These are not random checks. They are designed in advance.
Test execution means running the designed tests and comparing actual results with expected results.
During this phase, testers: • execute test cases • record results • report defects • retest fixes • perform regression testing when needed
Test case: Login with valid credentials
Expected result: User is redirected to the dashboard
Actual result: User clicks login, but the page freezes
This means the test failed, and a defect may be reported.
Execution shows how the software really behaves.
It helps answer: • does the product work as expected? • which scenarios passed? • which failed? • what defects were found? • what risks remain?
Test closure is the phase where testing activities are formally completed and reviewed.
This does not mean only “we are done.” It also means: • reviewing what was tested • checking what was not tested • summarizing results • documenting lessons learned • identifying improvement points
The team may: • check test coverage • summarize defects • evaluate whether exit criteria were met • create a test summary report • discuss what went well and what should improve next time
At the end of a release, the test closure report may say: • 120 test cases executed • 110 passed • 10 failed • 8 defects fixed • 2 low-severity defects remain open • payment and checkout fully covered • mobile tablet layout only partially covered • recommendation: improve test data preparation next cycle
This helps future projects too.
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