STLC Explained: Software Testing Life Cycle

The software testing life cycle (STLC) is sequence of phases your team follows to plan, build, run, and close testing for a release. The standard STLC has six phases: requirement analysis, test planning, test case development, environment setup, test execution, and test closure.

Every guide on this topic lists those six phases with same definitions. What they don't cover is how testing software life cycle actually works on a mobile team that ships weekly, where it breaks down, and what to do when one phase blocks rest.

What is software testing life cycle?

The software testing life cycle is a structured process that turns "we need to test this" into a repeatable system. Instead of ad-hoc testing before a release, STLC gives each phase a clear goal, specific activities, and a definition of done before moving to next phase.

STLC runs alongside software development life cycle (SDLC), not after it. The testing process life cycle starts when requirements land, not when code is ready. Teams that wait until build is done to start testing are already behind.

For mobile teams, STLC gets compressed. A 2-week sprint doesn't leave room for sequential, waterfall-style phases. Requirement analysis, test planning, and test case development often happen in same day. Environment setup means provisioning real devices. Test execution runs in CI/CD, not manually. The phases are same, but timing is different.

What are phases of software testing life cycle?

The phases of software testing life cycle follow a progression from understanding what to test all way through confirming that testing is complete.

Phase 1: Requirement analysis. The QA team reads requirements and identifies what's testable. On mobile, this includes checking whether a feature needs testing across both platforms, on specific device sizes, or under particular network conditions. The output is a list of testable requirements and any gaps that need clarification from product team.

Phase 2: Test planning. The QA lead defines testing strategy: what types of testing to run, which flows to automate, which devices to cover, and how testing fits sprint timeline. Test planning also sets pass/fail criteria for release. On mobile, this is where you decide whether to run on emulators, real devices, or both.

Phase 3: Test case development. Testers write test cases and automation scripts based on plan. For mobile teams, this phase includes writing tests that work across iOS and Android, accounting for platform-specific behavior. If your automation tool requires separate scripts per platform, this phase takes twice as long.

Phase 4: Environment setup. The team configures devices, OS versions, and infrastructure needed to run tests. On mobile, this is often biggest bottleneck. Getting a device lab running, connecting to a cloud device provider, or configuring emulators eats time that most STLC guides gloss over.

Phase 5: Test execution. Testers run tests, log results, and file bugs. This is where manual and automated testing both happen. Automated suites run in CI/CD. Manual testers handle exploratory testing and UX checks. On mobile, this phase includes regression testing across device configurations.

Phase 6: Test closure. The team reviews test results, calculates pass rates, documents defect metrics, and runs a retrospective on what went well and what didn't. This phase produces sign-off that says build is ready (or not ready) for release.

Each phase has entry criteria (what needs to be true before you start) and exit criteria (what needs to be true before you move on). In practice, mobile teams often blur these boundaries because sprint timeline doesn't allow for strict sequencing.

How does STLC relate to SDLC?

The software testing life cycle runs inside software development life cycle, not after it. SDLC covers full development process: requirements, design, coding, testing, deployment, and maintenance. STLC covers just testing portion of that process.

In a waterfall SDLC, STLC starts after development ends. Testing is a distinct phase. In an agile SDLC, STLC runs inside every sprint. Developers write code while testers write test cases. Execution starts as soon as code merges. The life cycle development process is compressed into days instead of weeks.

For mobile teams, relationship between SDLC and STLC matters because development cycle software teams follow determines how much time testing gets. If your team ships weekly, entire STLC needs to fit within that sprint. That's only possible if most of testing is automated and automation is reliable.

Where does STLC break down on mobile?

The standard STLC was designed for teams that ship quarterly. Mobile teams ship weekly or faster. That compression exposes failure points that most STLC guides never mention.

The first failure point is environment setup. Getting real devices provisioned and connected is slow. Teams that rely on physical device labs spend hours configuring devices for each test cycle. Cloud device providers help, but they add cost and can introduce network latency that makes tests flaky.

The second failure point is test execution. Regression in software testing is most time-consuming part of this phase on mobile. A regression suite that runs on one device isn't enough. The same suite needs to run across 8 to 12 device and OS combinations to cover your user base. If your automation framework uses selectors, those tests break every time UI changes. Your execution phase doesn't produce reliable results, and test closure phase can't sign off on build.

The third failure point is test case maintenance. The standard STLC doesn't include a maintenance phase, but it should. On mobile, test scripts degrade over time as UI evolves. Without ongoing maintenance, your test case development phase builds on a rotting foundation.

How does regression testing fit into STLC?

Regression testing is backbone of test execution phase. Every time your team ships new code, regression tests check that existing features still work. Regression testing in software testing catches bugs that new changes accidentally introduce.

On most mobile teams, regression test suite is largest automated suite. It covers login, core transactions, navigation, and flows most likely to break. A regression test failure in execution phase blocks release.

The problem is that regression testing on mobile is expensive. Each test needs to run on multiple devices. Each run takes time. If automation framework is fragile (broken selectors, flaky waits), regression results are noisy. QA leads spend closure phase triaging false positives instead of making release decisions.

Drizz changes this part of STLC. Because tests run on real devices using Vision AI instead of selectors, execution phase produces clean results. Regression tests adapt to UI changes automatically. The closure phase becomes a 10-minute review instead of a day-long triage session.

What does a mobile STLC look like in practice?

Here's how a mobile team running 2-week sprints can structure their STLC:

Day 1 of sprint: requirement analysis and test planning happen during sprint planning. The QA lead identifies testable requirements and maps them to existing automated tests or flags new tests that need writing.

Days 2 through 8: test case development runs in parallel with feature development. Testers write new test cases as features get built. Automated tests get added to suite as soon as feature is code-complete.

Ongoing: environment setup is handled once and maintained. Cloud device infrastructure stays provisioned. New OS versions get added to device matrix as they're released.

Days 9 through 12: test execution ramps up. The automated regression suite runs nightly. Exploratory testing covers new features. Bug fixes get verified.

Day 13: test closure. The QA lead reviews pass rates, confirms regression results, and signs off (or blocks) release candidate.

This only works if execution phase produces trustworthy results. If your regression suite is 20% false positives, you'll spend days 9 through 13 on triage instead of testing. Tools like Drizz keep execution phase reliable by running plain English tests on real devices with Vision AI, so regression results mean something.

How should you adapt your STLC for mobile?

Three changes make standard STLC work for mobile release cycles.

First, collapse sequential phases. On a 2-week sprint, requirement analysis, test planning, and test case development can't be three separate weeks. Run them in parallel with development.

Second, automate execution phase. Manual regression testing doesn't fit a weekly release cadence. Automate repeatable flows and keep manual testing for exploratory work.

Third, add a maintenance phase. The standard STLC ends at closure. Mobile STLC should include ongoing test maintenance between cycles. If you use a vision-based tool that adapts to UI changes, this phase gets much smaller.

The software testing life cycle works for mobile teams when you compress it, automate execution phase, and keep your test scripts stable. The six phases stay same. The timing and tooling change.

FAQ

What is software testing life cycle? 

The software testing life cycle (STLC) is a six-phase process that structures how teams plan, build, run, and close testing. The phases are requirement analysis, test planning, test case development, environment setup, test execution, and test closure.

What are STLC phases? 

The six software testing life cycle phases are: requirement analysis (identify what's testable), test planning (define strategy), test case development (write tests), environment setup (configure devices and infrastructure), test execution (run tests and file bugs), and test closure (review results and sign off).

How does STLC differ from SDLC? 

SDLC covers full development process from requirements to deployment. STLC covers just testing portion. STLC runs inside SDLC. In agile teams, STLC phases happen within each sprint rather than as a separate phase after development.

How does regression testing fit into STLC? 

Regression testing is part of test execution phase. It checks that existing features still work after new code changes. On mobile, regression suites run across multiple device configurations and are largest automated test set in most teams' STLC.

Why does STLC break down on mobile? 

Three reasons: environment setup with real devices is slow, test execution across multiple device configurations takes too long, and test case maintenance isn't included in standard STLC. Mobile teams need to compress phases and automate execution phase to keep up with weekly releases.

Can STLC work with agile sprints? 

Yes, but you have to compress it. The first three phases (analysis, planning, case development) run in parallel with development during sprint. Execution ramps up as code merges. Closure happens at end of sprint. The phases overlap instead of running sequentially.