What is the Software Testing Life Cycle? STLC Phases Explained

The software testing life cycle (STLC) is the structured sequence of phases — from requirement analysis through test cycle closure — that a QA team follows to validate a product before and during release.

Just as the software development life cycle (SDLC) guides how digital products get built, the STLC guides how they get validated. Different team members participate at each phase, so quality goals are met in a strategic, documented manner rather than left to a single pre-release check. Applause runs this process for enterprise teams, combining structured QA with real-world testing against the actual devices, markets and conditions customers use.

In this blog post, we break down the STLC phases, the challenges teams hit at each one and how the process has evolved to keep pace with modern release cycles.

What is the software testing life cycle?

The software testing life cycle is a sequence of tasks designed to understand the state of a system and make recommendations for improvement. The tasks that define STLC phases typically reflect the perspectives of stakeholders across the business to ensure all needs are met. Just as the software testing process incorporates many stages and functions, the STLC involves strategizing, planning, executing and completing test cycles.

In the past, software testing processes occurred shortly before product release as a way to ensure digital products don’t contain defects. These bugs negatively affect core functionality and the user experience. However, as digital systems became more complex and businesses released batches of software and apps more often, the STLC evolved. When organizations delay the software testing process to the end of the development cycle, the result is costly bug fixes and release delays. Software testing no longer waits until a product is fully developed. 

Over the last couple of decades, some organizations have included STLC phases before and during development to maximize resources. Some of the following tactics spread the software testing process and responsibilities:

• test automation
• test-driven development
• crowdtesting
• shift-left testing
• shift-right testing

An effective STLC produces more comprehensive and valid results than a traditional post-development testing stage. This process helps organizations make changes that ultimately drive customer satisfaction and higher revenue. Completing these STLC phases is not a pre-release burden. It’s an effort to discover key insights that will benefit the business over the short and long terms.

What are the differences between the SDLC and the STLC?

While the software development life cycle (SDLC) is designed for developing digital products, the STLC is for validating them. Various team members participate in software testing processes at different stages. These efforts help businesses achieve their quality goals in a strategic, documented manner.

What are the 6 key phases of the STLC?

The software testing life cycle provides confidence in a software release. It delivers that confidence through a series of tasks that take validation through ideation to design and execution.

Each STLC phase is useful in its own way to achieve high-quality software releases. Likewise, each STLC phase comes with its own goals and deliverables, all intended to catch defects and optimize test coverage.

Let’s dig into these software testing life cycle (STLC) phases:

1. Requirement analysis

Most development initiatives begin with software requirements that specify what the business expects from the project. Software requirements often include high-level business needs, architectural requirements that detail how the feature will be designed and supported, and detailed system requirements from which developers build the product. System requirements include functional and non-functional specifications, both of which present opportunities to test and validate.

In this STLC phase, testers work both within their own teams and cross-functionally to contextualize how they will test the software. Requirement analysis often includes brainstorming sessions to identify blind spots. The team then prioritizes certain assessments to ensure all requirements are covered. Techniques like mind mapping to visualize relationships between requirements and root cause analysis to identify potential issues early occur in this STLC phase.

When in doubt or lacking requirements documentation, the QA team will question the engineering or business side. This helps clarify and solidify a testing strategy. Thus, software testing processes begin before a single test executes.

Common challenges in the requirements analysis phase of the STLC include:

• incomplete or ambiguous requirements, which can lead to misaligned expectations and testing goals
• difficulty in obtaining stakeholder buy-in, which can slow down the analysis process
• lack of documentation, making it hard for testers to establish clear objectives

2. Test planning

The second STLC phase guides much of the work to follow. Test planning takes the insights found during requirements or product analysis and turns them into a documented QA strategy.

The test team leadership determines what resources and efforts will evaluate the release. The resulting test plan documentation both informs testers and other departments how the testing work will begin. A good test plan often includes sections such as:

• risk analysis
• backup plans
• resource allocation
• test environment details
• criteria for success

This plan is especially helpful if other members of the organization will take part in testing and bug remediation, such as developers executing unit tests and writing hotfixes.

The plan spells out several details of the software testing processes to be undertaken. Test plan details often include the scope, objectives, types of functional and non-functional tests (both automated and manual), and details for the test environments. Once these details are determined, test management sets roles and timelines for the work. Finally, the testing team can determine what deliverables it will provide upon completion of the STLC phases.

Common test planning challenges in this part of the software testing process include:

• estimating the time and resources required, which can lead to timeline overruns
• defining the scope of testing, particularly in large projects where multiple components and integrations need coverage
• aligning test plans with constantly changing requirements, especially in Agile environments where requirements may evolve frequently
• balancing automated and manual testing resources to ensure optimal efficiency and coverage.

3. Test case design and development

With the test plan in place, testers can begin to write and create detailed test cases. In this STLC phase, the QA team fleshes out the details of the structured tests they will run, including any test data they will need to facilitate those tests. While tests must ultimately validate the areas defined by requirements, testers can apply their skills and creativity in how they achieve this task.

When conceptualizing test cases, the tester’s goal should be to validate functionality within the allotted time and scope. Core functionality takes the highest priority. Test cases should be simple, understandable and unique. Aim to achieve full coverage of the requirements in the specifications document. A traceability matrix can help link requirements to their corresponding test cases, ensuring that all requirements are adequately validated in the software testing process and nothing is overlooked. This helps maintain accountability and provides a clear overview of test coverage.

Test cases must be identifiable and repeatable, as developers will add new functionality to the product over time, requiring tests to run again in future iterations of the software testing process. They must also not alter the test environment for future tests, especially when validating configurations. Test cases might also require maintenance or updates over time to validate both new and existing functionality. This work also occurs at this STLC stage.

Once test cases are ready, a test team lead or peer can review them. They might also review and update automated test scripts at this STLC stage. Ultimately, the team prioritizes and organizes these test cases into test suites that run later.

Test case design and development challenges might include:

• updating test cases as requirements change, a difficult task that requires continuous coordination with development teams
• ensuring test cases are reusable and maintainable for future iterations, especially in Agile environments where changes are frequent
• identifying edge cases missed by requirements
• balancing the level of detail in test cases to make them understandable while avoiding rigidity

4. Test environment setup

The test environment provides the setting where the actual testing occurs. This is a crucial software testing life cycle phase, and it requires help from other members of the organization. Testers must have access to bug reporting capabilities, as well as the application architecture to support the product. Integrating bug tracking with project management tools enhances communication and workflow efficiency in the STLC. Ensuring that issues are tracked, prioritized and resolved helps foster a coordinated approach to software testing. Without these elements, the software testing process can hit a standstill.

Once ready, testers establish the parameters for the test environment. The team defines the hardware, software, test data, frameworks, configurations and network for the environment. In this STLC phase, testers adjust these environment parameters depending on what the test case requires. For example, the majority of a product’s users might be on an Android device, use a certain version of a Chrome browser, and have a certain amount of processing power on those devices—these are parameters the test environment would include.

Smoke tests within these test environments provide a very early and initial check that the software is ready for more comprehensive testing. These smoke tests often include basic login functionality, essential navigation paths and verification of critical services. These smoke tests against the builds are part of the deliverable in this STLC phase.

The test environment setup phase includes challenges like:

• ensuring environment parity with production to prevent discrepancies that conceal defects
• managing different configurations and setups, which can be complex for multi-platform applications
• sourcing and maintaining the necessary test data, which must be consistent and representative of real-world scenarios
• handling dependencies on external systems or services, which may require virtualization or stubbing to simulate expected conditions.

5. Test execution

Next in the software testing life cycle, it’s time to fully test the product. At this STLC stage, testers execute all of the test cases, or as many as is possible within the allotted time. QA professionals and automated scripts execute a number of functional and non-functional tests.

Here in the STLC, testers will identify and report detailed bugs that arise from test case execution. From there, they log the system’s performance compared to its requirements. As developers make fixes, testers often retest the product. This software testing process, known as regression testing, ensures that the fixes do not introduce new issues elsewhere in the application. In Agile environments, changes are frequent and rapid. Regression testing helps maintain software stability and quality throughout these frequent changes. During test execution, the number of tests can pile up. Test automation helps achieve necessary coverage and velocity.

Challenges in the test execution phase of the STLC include:

• managing flaky automated tests, which lead to unreliable results and complicate defect analysis
• ensuring sufficient test coverage within the time constraints, especially for complex or large-scale systems
• balancing manual and automated testing efforts to achieve efficient, yet comprehensive coverage
• effectively managing retesting and regression testing to confirm that bug fixes do not introduce new issues

6. Test cycle closure

The final STLC phase is test cycle closure. During this stage, the testing team provides a test closure report summarizing its findings. This report typically includes overviews of the testing work and results, an assessment of the testing, and the manager’s approval.

During the test cycle closure, the testing team checks its deliverables. Closure details relevant to the testing work include the test strategy, test case documents, automated test scripts and test results. The team will then complete and close incident reports, which detail unusual or unexpected behavior that the test team observes during testing. The team must also archive the resources it used during testing, such as scripts, tools and environments, for later use.

From there, the organization plans the product for support and release, which often includes acceptance and feedback from customer representatives. Communication is key in this STLC phase, as additional perspectives might uncover a quality, cost, or coverage issue that the rest of the group missed. These discussions can yield additional analysis or inform how to improve QA work in the future. In this way, the software testing process never truly ends. Remember, it's a cycle.

Test cycle closure challenges include:

• capturing and analyzing all relevant testing metrics to ensure process improvement
• coordinating feedback from multiple stakeholders to address quality gaps before release
• ensuring that all testing resources, such as scripts and environments, are properly archived for future use
• communicating lessons learned to prevent repeated issues in future cycles

How Agile affects the software testing life cycle

The common software testing life cycle phases above follow a sequential approach similar to Waterfall application development. However, as many businesses rethink how they develop products, testing must also adapt to align with iterative organizational practices and pace of releases.

The QA team might follow an Agile testing method instead, which impacts the STLC phases above in various ways. For instance, Agile encourages continuous collaboration, iterative development and ongoing testing. That means that the traditional linear approach must be modified to support more fluid and overlapping STLC phases. This fluidity in the software testing process helps ensure faster feedback loops, earlier bug detection and alignment with evolving requirements. 

Additionally, Agile testing places an emphasis on shift-left and shift-right testing to reduce QA bottlenecks. While test automation is included in the STLC phases above, Agile testing might place a higher priority on methods like in-sprint testing and test-driven development, both of which generally result in cleaner, simpler bits of code. Production testing, or shift-right testing, helps the QA team identify defects after the test cycle closure. While these defects are often more costly to correct, it’s better late than never when it comes to fixing a bug. Shift-right often involves exploratory testing and user testing to find defects that test cases failed to uncover.

In short, the STLC phases above might change slightly depending on the organization’s development and testing philosophies.

Make your software testing life cycle more efficient

Running the STLC well takes more than a defined process. It takes the people and infrastructure to execute it at scale, especially as release cycles compress. Many teams reach a point where staffing, device coverage or market-specific testing outpaces what an internal QA team can cover alone.

Applause works as a strategic testing partner across every STLC phase, from requirement analysis through test cycle closure. That means QA testing services, real-world testing across the actual devices and markets your release needs, and test automation support — so your team can focus on what to test rather than how to staff and run it.

Applause fits within the scope, timelines and priorities you've already defined, or helps establish them from the outset. Whether that's an automation framework, manual testers in a specific market, or support with shift-left testing, Applause works within your existing STLC rather than replacing it.

Talk with Applause about making your software testing life cycle more efficient.

What is the software testing life cycle?

The STLC is a documented sequence of tasks that a QA team follows to validate a software release. It contains six phases: requirement analysis, test planning, test case design, test environment setup, test execution and test cycle closure.

How is the STLC different from the SDLC?

The SDLC (software development life cycle) governs how a product gets built; the STLC governs how it gets validated. The two run in parallel, with STLC phases increasingly starting before development finishes rather than only after.

Does Agile eliminate the STLC phases?

No. Agile compresses the STLC phases into overlapping, repeating cycles within each sprint rather than one linear pass at the end of a project.

Does Applause provide QA testing services for the STLC?

Yes. Applause provides real-world testing services across the STLC, working within a team's existing testing priorities, scope and timelines, or helping define them.