The Software Testing Life Cycle (STLC) Guide: Phases And Criteria


What is the software testing life cycle (STLC) and how important is it?

No matter how innovative or attractive a software application might be, it will be abandoned by users if they encounter glitches or bugs. Software development companies recognize the vital role of testing for launching first-rate products. The STLC is the process of analyzing a computer program or mobile app to make sure it meets the requirements of the business and users, and to verify the overall quality of the product. The whole purpose of the STLC is releasing a bug-free software, with a focus is on diagnosing bugs and fixing defects. Testing has been integrated into the Software Development Life Cycle (SDLC) and goes now hand-in-hand with software development throughout the whole building process.

Find out more about the different types of software development on our blog.

Since testing is also a structured and standardized process, it follows a life cycle similar to the SDLC. Testing has steps that need to be executed in a defined sequence. The STLC improves consistency in testing operations and ensures that enough tests have been performed to verify that the software functions as intended.

Here because you have a budding interesting in software testing? Find out more about how to become a software tester.


SDLC and STLC: What’s the difference?

The software development life cycle is a framework that defines the steps involved in the development of software at each phase. The SDLC covers the complete cycle of development including planning, creating, testing, deploying and maintaining a software product.

The software testing life cycle is systematic testing procedure defining a sequence of specific activities conducted during the testing process. The STLC is responsible for creating tests adapted to the requirements collected by SDLC and for verifying that features meet those requirements.

The SDLC and the STLC are closely related to each other, but they simultaneously pursue different tasks to complete the same goal – client satisfaction and releasing fully functional software.

It is important to know that the Agile testing methodology process is not sequential (executed only after a coding phase) but continuous. Testing can begin at the start of the project with ongoing integration between development and testing. Executing testing during the implementation reduces development time.


Read on: Agile Software Development: Definition, Manifesto, Framework, And Benefits.

What are the Software Testing Life Cycle phases?

The STLC consists of six interconnected sequential phases. Each of them has a definite entry and exit criteria, activities and deliverables. The entry criteria specify the prerequisite items that must be completed before the testing phase can begin, while the exit criteria define the items that must be completed before testing can be concluded.

Need some help checking off the tasks you need to do during the software testing life cycle?

Download our software testing life cycle checklist here.


Phase 1: Requirement analysis

During this phase the software project feature requirements collected in the SDLC process are evaluated to identify testable aspects. These requirements can be functional or non-functional. The ability to automate testing is also evaluated. At this stage any requirement ambiguity will be clarified with stakeholders.

Entry criteria:

  • Documented requirements
  • Acceptance criteria
  • The software’s architectural goals and specs


  • Identify testing elements, functions and features
  • Define approval criteria
  • Draw an RTM
  • Identify the test environment details where testing will be carried out

Exit criteria:

  • Approved requirement traceability matrix (RTM)
  • Automation feasibility report (if applicable)


Phase 2: Test planning

During this phase, the test strategy is outlined in a test plan document. This strategy includes tools needed, testing steps, roles and responsibilities. Part of this strategy is a risk assessment, cost analysis and an estimated timeline for testing.

Entry criteria:

  • Requirement analysis
  • RTM
  • Automation feasibility report


  • Selecting a program’s testing framework (modular, data-driven, keyword-driven, Hybrid, or Library Architecture Testing Framework etc.)
  • Estimating the expenditure
  • Preparing a test-strategy document
  • Establishing resource management, positions and responsibilities

Exit criteria:

  • Approved test plan including timelines and risk/cost analysis

Related: Why You Should Consider TaaS Before Launching A Product.


Phase 3: Test case development

Test cases are created during this phase. Each case will define test inputs, procedures, execution conditions, and expected results. Any necessary automation scripts are also created. Test case development supplies test protocols, expected fallouts, and a predicted finish date for every test case. 

Entry criteria:

  • Approved test plan including timelines and risk/cost analysis
  • RTM


  • Developing a software testing case
  • Review and baseline test cases and scripts
  • Creating test data 

Exit criteria:

  • Approved test cases
  • Automation scripts


Phase 4: Test environment setup

During this phase, testing environments are configured and deployed. Sometimes test servers are set up. Test environment setup determines the software and hardware conditions under which a product is tested. The test team does not have to be involved if the development team provides the test environment, but it is required to do a readiness check (smoke testing) of the given test environment.

Entry criteria:

  • System design
  • Project architecture definitions


  • Understanding the required architecture, environment set-up and prepare hardware and software requirement list for the test environment.
  • Arranging features and test ecosystems.
  • Performing the smoke test on the build

Exit criteria:

  • Environment ready with test data set up
  • Smoke test results


Phase 5: Test execution

During this phase, features are tested in the deployed environment using the established test cases. Expected test results are compared to the actual ones and results are gathered to report back to development teams. The process consists of test script execution, test script maintenance and bug reporting. Practical testing will establish whether the product satisfies the user’s and organization’s expectations. Non-practical testing ascertains whether the system behaves to the customer’s standards.

Entry criteria:

  • A fully configured testing environment
  • Test design
  • RTM timetables
  • Evaluation scripts
  • Smoke test
  • Testing record


  • Testing is performed, based on ready-made test documentation
  • Reporting system flaws
  • Relating RTM
  • Retesting fixed defects

Exit criteria:

  • All tests are executed and results documented


Phase 6: Test cycle closure

In this last phase of the Software Testing Life Cycle, a test result report for the client will be prepared. It should summarize the entire testing process and include the percentage of defects found to positive test results, the time spent on testing, total cost and the total number of errors found and fixed. The cycle can be closed manually or by using project management tools.

Entry criteria:

  • Final documents
  • Testing records


  • Test closure report for the client
  • Evaluating cycle completion criteria based on time, test coverage, cost, critical business objectives and quality
  • Preparing test metrics
  • Test result analysis to find out the defect distribution by type and severity.

Exit criteria:

  • Test closure report
  • Test metrics


The Software Testing Life Cycle is a crucial part of software development. The STLC helps to identify which tests are necessary to improve the quality of software and which are redundant. Implementing the STLC significantly improves workflow by defining and refining each step of the testing process. It might surprise you that there are over 100 different types of testing, which answers the question as to why implementing the STLC is so important.

At Rare Crew, our expertise doesn’t stop at custom software development. Our software testing teams are here to help you identify any issues in your software development life cycle so that your software can be delivered at peak performance, on time, to your satisfaction.

Rare Crew is always on the lookout for skilled testers, both experienced and just making their way into the industry. Do you think you might fit the job? Learn more about what we do.




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