Software Testing Lifecycle (STLC)

STLC, short for “Software Testing Life Cycle”, is the process followed to ensure that a software meets its quality and testing goals. This guide talks in detail about STLC and tries to clear any related doubts.

Software Testing Lifecycle (STLC) is a way for testers to follow a series of steps to deliver a bug-free application that stays true to the user requirements. STLC in testing is a systematic approach with the objective of meeting software quality requirements. While it sounds similar to Software Development Lifecycle (SDLC), it differs largely from the concept. Both SDLC and STLC are two different methods in IT, and we will mention their differences in the later section. We will discuss more on this topic and define all the related terms to STLC. Let’s begin.

What is Software Testing Life Cycle (STLC)?

STLC is a systematic approach to testing, which involves verifying an application to check if it meets the requirements and is free of faults. It follows a series/phase of steps where every phase has its objective and deliverables, and the software must fulfill those goals to move on to the next step. The purpose of STLC in testing is to provide a high-quality, reliable, and stable application that stays true to the requirements of the customers. The phases of STLC are Planning, Analysis, Design, Environment Setup, Execution, Closure, and Defect Retesting. We will discuss each one of these steps in detail in the coming sections.

What Is the Role of Software Testing Life Cycle?

The role of STLC is primarily to identify issues in the application as soon as possible and record it for developers to understand and resolve. For testers, STLC assists in the following:

  • Fine-tuning the agile process, making it effective and efficient for cross-team communication
  • Clearly defining the deadlines for project testing
  • Properly documenting the goals and objectives of every project and following through consistently
  • Ensuring and verifying that the objectives of all the phases are accurately met
  • Testing each and every feature of the software before passing it for adding more features
  • Analyzing the tasks that can be automated to improve the testing quality

Here are some of the common activities in STLC that you would have to execute:

  • Analyzing all the requirements of the project
  • Creating a document that measures the progress of the testing
  • Identifying the testing types and techniques you need for the project at hand
  • Determining which environment to test your application on
  • Prioritizing the right tasks and understanding which of those can be automated
  • Listing down the automation tools you need to run your STLC tests

Some of the popular automation tools you can use are Testsigma, Selenium, Cypress, and TestNG. All of these have different features and provide varying services to your testing needs. You can choose the one that complements your project.

Advantages of STLC

Some advantages of STLC are:

  • Helps design meaningful tests that ensure the quality of software applications
  • Improves customer satisfaction and business success
  • Makes it easy to track the progress of the project with proper documentation and its systematic approach
  • Provides a faster testing process to help teams identify issues at the earliest possible testing stage
  • Supports shift left testing principle

STLC vs SDLC: How Do They Differ?

Both STLC and SDLC are related to software development and are two critical parts of software development, but they differ in their goals. STLC singularly pertains to the entire testing phase that is a part of the SDLC life cycle. You can perform STLC either within SDLC or alongside it. The key difference between the two is their functioning; SDLC undertakes the complete structure of planning, designing, creating, testing, and deploying the software, whereas STLC develops and executes the tests created to validate the user requirements gathered as part of SDLC.

What are Entry and Exit Criteria in STLC?

STLC must comply with entry and exit criteria to be termed as successful. Ideally, the QA team takes care of this point and only begins/completes the next STLC phase after both criteria are met. Both these criteria are defined for each phase of STLC.

Entry Criteria

Entry criteria for an STLC phase are to undertake all prerequisite conditions that must be met before testing starts. All the documents, with the necessary information regarding testing, should be available before initiating any of the STLC phases. For example, to begin with, creating test cases, you must have the user requirement document, a complete understanding of the application flow, and the test plan document. This is the entry criteria for developing and executing test cases.

Exit Criteria

Exit criteria are all the information/items that must be available and completed before concluding a phase. It includes all the actions, tasks, documents, and test elements that need to be over before marking the phase complete and moving on to the next one. One example of exit criteria can be verifying if the user requirements are proper and all the risk-associated areas of an application are thoroughly tested.

The Six Phases of STLC Phases

STLC Phases
STLC Phases

STLC consists of 6 phases where each has its entry-exit criteria and comes with associated activities and deliverables. Entry-exit criteria define when the phase starts and ends. Activities and deliverables define the actions taken within the phase and the results received. You can execute some of these phases together while others run more independently. These are the 6 phases of STLC:

Requirement Analysis

It is the first phase of STLC which deals with the QA team analyzing and understanding the requirement document to start the testing process with accurate information.In the Requirement analysis phase, the entry criteria are requirement documents, acceptance criteria, and understanding of the product architecture. The exit criteria for this phase are approved Requirements Traceability Matrix (RTM) and automation feasibility reports that evaluate if the tests can be automated. All of this ensures that the testing process starts with the right information and focuses on the important areas of the software.

Test Planning

After determining the user requirements, the next phase of STLC is to plan the tests. It is a critical step of STLC where all the test plans are defined, and a detailed strategy is laid out for the project. It includes developing test steps, assigning roles and responsibilities, and choosing the right testing approach and automation tools, if any. The QA team also calculates the estimated cost and resources to begin the testing.The entry criteria for the test planning phase are approved Requirements Traceability Matrix (RTM) and automation feasibility reports. The exit criteria are approved test plans, automation scripts, and defining the cost analysis of the complete project.

Test Case Development/Design

After finishing the planning stage, this phase is designing and developing the test cases. In this step, the testing team creates the test steps with proper input, test execution conditions, and expected output for execution.For the test case design and development phase, the entry criteria are approved test plans, automation scripts, and defining the cost analysis of the complete project. The exit criteria are the approved test cases and automation scripts with the proper information for each test step.

Test Environment Setup

This phase includes setting up a test environment to run your test cases and check the application for its efficiency. It decides the conditions to test your application and involves configuring and deploying the test environment. Often, this step also includes setting up test servers. You can either perform the test environment setup in sequence or execute it after the requirement analysis phase, as it is independent of all the previous phases.The entry criteria of this phase are requirement documents, system architecture details, and application design. The exit criteria are a fully up-and-running test environment to execute the approved test cases.

Test Execution

After all the setup and planning are over, the test execution phase comes. The QA team runs the test cases and scripts to check the quality of the application. They compare the expected results with the actual results to understand which areas have issues and need attention.The entry criteria of this step are the combined exit criteria of all the previous steps, including test plans/cases, test environment, user requirement document, and more. The exit criteria are all the executed test cases with results.

Test Closure

The last phase of STLC is test closure which pertains to preparing a test result report. It summarizes the testing process and highlights the comparison between the actual and expected test results. The comparison includes the fulfilled project objectives, time taken to complete the testing, budget, test coverage, and identified issues.The entry criteria for the test closure phase are test results after executing all the test cases. The exit criteria are designed, delivered, and approved test results report.

Characteristics of STLC

STLC characteristics define the scope of testing and its importance as a part of SDLC. Here are some of them:

  • STLC is a fundamental section of SDLC, but it only consists of testing phases.
  • The phases of STLC start soon after requirement documents are defined.
  • STLC follows a series of steps in a sequential manner to yield quality software that functions as per the requirement document.

In STLC, before starting any phase, you will have to analyze and define the scope of testing, the entry and exit criteria, and the test cases. All this helps to decrease the test cycle time and enhance product quality. And after the development phase is complete, the testing team can begin the execution using the test cases.


Quality software is important for the business as well as for the users. And STLC in testing ensures that every application you deploy is free of bugs and ready for users. STLC is a series of steps for testers to follow to begin the testing and complete the project on time with minimum issues.There are multiple advantages to STLC and why it is important in testing. There are primarily 6 phases in STLC that govern the testing process and determine the quality of the application. We have discussed all the steps above.One of the best ways to execute the STLC method is to adopt test automation where it is possible to remove redundancies and reuse the test cases. Automating the testing further helps record the results and accurately locate the issues in the applications.For all your automation testing needs, give Testsigma a chance. It is a no-code, AI-powered, cloud-based test automation that supports web, mobile, and API testing. Book a free demo now to see the tool in action.

Frequently Asked Questions

What are the 7 steps in the software testing life cycle?

What are the principles of STLC?