| STLC activity | What happens | Planning use |
|---|---|---|
| Requirement analysis | First STLC phase. Test planning is expected to start as soon as requirements become available. | Bring testers in when requirements are drafted, not when a build exists. |
| Test planning | Requirement insights become a documented test strategy. The test plan outlines scope, objectives, schedule, resources and deliverables. | Agree the plan before test cases are written. |
| Test case development | Testers create detailed test cases based on requirements and aim to cover all aspects of functionality. | Check that every requirement has a test case behind it. |
| Test environment setup | Sits between test case development and execution. | Plan it as a distinct step rather than assuming it happens by itself. |
| Test execution | Tests run against the build. Test automation can be used to increase test coverage. | Decide which repeated checks are worth automating. |
| Test closure | Final phase of the STLC. | Close only against exit criteria that were agreed earlier. |
Phase names and activities follow ACCELQ’s software testing life cycle guide and testRigor’s STLC overview.
Software development life cycle testing runs across the whole SDLC rather than as a single closing step, and it works best when each phase has defined entry and exit criteria before testing begins.
For the wider picture of how teams plan, build and ship, start with our software development guide. To see how each stage of delivery fits together, read Phases Of The Software Development Life Cycle: A Practical 2026 Guide To Building Reliable Software – Interestingdevelopment.
What late or fragmented testing costs
Testing that starts late or runs in disconnected pieces makes defects more expensive to deal with. AppSierra’s overview of the SDLC testing phase puts it plainly: the longer detection of issues is delayed, the greater the cost you are likely to face. HeadSpin’s discussion of early testing describes the aim of moving testing earlier as locating and fixing issues before they become more significant and costly.
Each common pitfall points to a specific consequence:
- Testing left until the end. Defects found late are the ones most likely to carry the higher cost described above, so a final test phase on its own is a weak plan.
- Weak test design. According to testRigor, poor test design can fail to identify bugs in the application, so a large number of executed tests does not prove the right things were checked.
- Isolated tools. LeadDev’s article on full SDLC testing describes testing as fragmented when tools are isolated and do not inform each other of a holistic strategy for quality.
- Testers separated from developers. In shift-left testing, testers collaborate with developers and other stakeholders from the very beginning, which is the opposite of handing over a finished build.
Decisions that continuous testing changes
The software testing life cycle emphasizes continuous testing throughout development so that bugs and defects are caught early. That shifts several planning choices.
- When testers join. Schedule testers into requirement discussions. Planning can only start once requirements exist, so late involvement delays everything that follows.
- What to automate. Use automation to widen coverage during execution. It suits checks that run repeatedly, while judgement-heavy checks stay with people.
- How often tests run. Continuous integration merges code changes into a shared repository frequently, with automated builds and tests validating each change. Teams that adopt it get feedback per change instead of per release.
- Which test types you need. Unit-level and regression-level checks answer different questions. The guide to Unit Testing Vs Regression Testing: When, Why, And How To Use Each In 2026 – Interestingdevelopment compares them so you can decide what runs on every change.
How testing maps across SDLC phases
The STLC runs through six phases: requirement analysis, test planning, test case development, environment setup, execution and closure, according to ACCELQ. Software testing is not a one-time activity but a series of activities performed across the entire SDLC. What links the phases is the handoff: each one produces something the next depends on.
From requirements to a test plan
The first handoff passes requirements to the testing team. Testers are expected to begin planning as soon as the requirements become available, and QA testers are involved in multiple goal-oriented activities from that point. The return handoff is the test plan and strategy. Test planning converts the insights from the requirements phase into a documented test strategy, so a vague requirement becomes a vague plan. Raise unclear requirements with the people who wrote them before cases are drafted.
From test cases to execution
Testers create detailed test cases from the requirements and make sure they cover all aspects of functionality. Developers then deliver builds, and in teams using continuous integration each merged change triggers automated builds and tests. During execution, automation increases coverage, so manual effort can go to scenarios that need human judgement. The handoff to check is the build itself: if testers receive something they cannot exercise, the earlier steps lose their value.
Defects and closure
Defects found during testing are reported, tracked, fixed and retested until they reach the quality standards defined in the SRS. This loop passes work back and forth: testers report to developers, developers return fixes, and testers retest. Closure is the final STLC phase, and it should be a deliberate stop against agreed criteria. In modern delivery models, AppSierra notes that testing activities are involved in most stages of the SDLC, so closure of a test cycle does not mean testing was absent elsewhere.
Building a test strategy
A test strategy turns requirement insights into decisions about what to test, with which tools, and when testing is finished. The testRigor guide says the strategy defines the types of tests needed, such as functional, performance and security testing, and any specific tools required. The test plan document then outlines scope, objectives, schedule, resources and deliverables.
- Choose test types from the requirements. If a requirement concerns speed or protection of data, a functional check alone does not cover it. Performance and security testing belong in the strategy for those cases.
- Set entry criteria. These are the conditions that must be fulfilled before testing activities can begin. They stop teams from starting execution on work that is not ready.
- Set exit criteria. These are the conditions that must be met to conclude the testing phase successfully. Agree them up front so closure is a check, not a negotiation.
- Build feedback loops. LeadDev lists consistent feedback loops across teams as a way to improve collaboration, which also helps keep tools and results joined up.
Where a team has a single tool and a small scope, a short plan with clear criteria is enough. The more teams and tools involved, the more the feedback loops matter.
Frequently asked questions
How is the software testing life cycle related to the SDLC?
The STLC is a part of the SDLC and restricts its activities to the software testing part. It is the sequence of activities performed during the testing process.
What does a requirement traceability matrix do?
It links requirements to test cases, which ensures test coverage and enables traceability.
Does testing end at release?
Not entirely. After a product is released, maintenance is performed for the existing customer base, and in modern models testing activities are involved in most SDLC stages.
