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Difference between SDLC and STLC

SDLC (Software Development Life Cycle) and STLC (Software Testing Life Cycle) are two diverse fundamental procedures in the QA and software development domain. While Software Development Life Cycle focuses on the entire development and deployment of a software product, Software Testing Life Cycle specifically addresses the test processes and activities involved in certifying the reliability as well as the quality of the software.

This guide article aims to give an in-depth understanding of the differences between SDLC and STLC, their phases, and when to use them in order to deliver reliable software solutions.

What is SDLC?

SDLC is the backbone of software development. It is a comprehensive framework that defines all the standard stages included during the software development process. It outlines the various stages such as planning, requirement analysis, and gathering, software designing, execution of designs and new methods, testing, deployment, and maintenance.

Crucial Traits of SDLC (Software Development Life Cycle) 

  • Comprehensive documentation of the model structure and functions, along with the outcomes of tests, are accessible.
  • The project can be finished step-by-step, with every single unit being identifiable and different before moving on to the subsequent phase.
  • A robust risk management approach/ tactic is used to decline risk exposure.
  • A clear comprehension of the responsibilities and roles of business analysts, project managers, software developers, and designers.
  • Timely, lucrative, and achievable outcomes.

Phases of SDLC

The crucial phases of the Software Development Life Cycle (SDLC) are as follows:

  • Requirements Gathering and Analysis: During this phase, development teams and project stakeholders collect and scrutinize the requirements for the software project. The main objective is to understand the expectations and necessities of the end-users or customers.
  • Design: In this phase stage, the system elements, software architecture, and UI (user interface) are planned and documented. The design phase helps create a blueprint for the development process. 
  • Implementation (Coding): This stage includes the actual software development based on the design specifications. Developers write the code following best practices and coding standards.
  • Testing: The testing phase mainly aims to detect and fix defects/ glitches in the code. Various forms of testing, like system testing, integration testing, and unit testing are directed to ensure that the software functions as proposed.
  • Deployment: Once the software product has passed all testing stages and meets the necessary quality standards, it is released or deployed to clientele or end-users for use.
  • Maintenance: The maintenance phase mainly involves giving ongoing updates, support, and bug fixes to the software product to guarantee its sustained smooth operation.

Phases of SDLCWhy Use SDLC?

Let us take a glance at some of the core reasons for using the SDLC approach/ method:

  • It aims to deliver a superior quality software system that assists you to meet the user/ client expectations
  • After the completion of every single stage, a formal review is performed, ensuring optimal management control. 
  • SDLC allows the creation of comprehensive system documentation.
  • It creates numerous intermediate products that can be reviewed to confirm they meet consumer needs and comply with standard requirements.
  • It also ensures that system requirements are traceable back to the stated business requirements. 
  • Each stage in SDLC has well-defined deliverables, entry, as well as exit criteria. 
  • SDLC follows a sequential development method, making it the perfect model for small or mid-sized businesses with clear requirements.

What is STLC?

The STLC (Software Testing Life Cycle) is cyclical and an iterative procedure that has the purpose of preventing loopholes/ errors in the software. Usually, the STLC counts analysis, planning, designing, setup, implementation, and test-ending activities. It comprises a suite of activities to confirm the standard quality of the software app as part of the test process. The STLC guarantee that every new release rolls out easily and successfully.

Crucial Traits of STLC (Software Testing Life Cycle)

  • Scrutinizing system requirements collected from stakeholders and customers. 
  • STLC assists in the formation of a traceability matrix, an essential document in software development used for tracking project requirements and confirming they are being met.
  • Defines the testing technique and type.
  • STLC prioritizes the most significant features for testing.
  • Defines the test implementation environment.
  • STLC assesses the automation feasibility, through the checklist that includes multiple factors to evaluate whether to automate a test case.
  • After the development stage is ended, QA’s can execute the test cases, aiding in the prompt detection of bugs.

Phases of STLC

The phases of the Software Testing Life Cycle (STLC) are as follows:

  • Requirements Analysis: During this stage, the BRD (business requirements document) formed in the SDLC requirements stage is analyzed by the QA team so that they comprehend the key functionality and outcomes that are needed from the newest system.
  • Test Planning: Once the functionality and results are understood, the QA team will commence planning how they are going to plan their tests. The test planning stage includes generating a comprehensive test strategy & plan. Test scope, objectives, timelines, as well as resources are defined in this phase. It lays the foundation for the complete test procedures.
  • Test Design: In this particular phase, test scripts and test cases are designed based on the software requirements & design. QA engineers create test cases to check the functionality and confirm the complete test coverage of the software.
  • Test Execution: This stage counts running the test scripts and cases on the software. Testers implement the tests and record the outcomes. Bugs or issues found during tests are logged for further examination and resolution.
  • Defect Reporting & Tracking: In the defect reporting and tracking stage, QA’s report the recognized defects in a defect tracking system. The errors/ defects are assigned to develop (development) team for fixing. QA engineers then track the defects’ status and validate fixes after they are executed.
  • Test Closure: In the test closure stage, the test outcome is prudently scrutinized and test summary reports are prepared. The expert QA team assesses whether the software meets the test goals and if it is all set for deployment. The test summary reports are then presented to stakeholders for review.

Phases of STLCWhy Use STLC?

Let us take a glance at some of the core reasons for using the STLC approach/ method:

  • Software Testing Life Cycle (STLC) helps make the tests process highly effective, consistent, and sophisticated.
  • Milestones and deliverables can be incorporated for every single stage of the project. 
  • The model is designed to be easily executable and understandable, even if expanded to several levels.
  • Time constraints are perfectly incorporated into project formulation.
  • Every single module of the project is well-tested before the commencement of another module.
  • The particular project requirements are compared to the actual results achieved.

Difference between SDLC and STLC

OriginDevelopment Life CycleTesting Life Cycle
DefinitionSDLC produces a superior-quality system that exceeds or meets users’ expectations, works excellently and competently in the current, planned, and strategic information technology infrastructure, and is lucrative to manage.STLC, on the flip side, identifies what test actions to perform and when to achieve those test activities. Although tests distinct between Organizations, there is a specific test life cycle.
FocusOn both dev (development) as well as the test process.On merely testing process.
PerformedThe stages of the SDLC are ended before those of the Software Testing Life Cycle (STLC).The stages of the Software Testing Life Cycle (STLC) are performed after the stages of SDLC.
ObjectiveAll through the SDLC procedure, the aim is to overcome any obstacle on the way to effective/ successful software development.On the other hand, a test is just intended to detect pitfalls or weaknesses in the system.
Relationship with Other Life CycleSDLC is taken as the predecessorSTLC is taken as the successor
Team InvolvedProject Managers, Business analysts, Designers, and Developers, are involved in SDLC.Quality assurance and Testers teams are involved in Software Testing Life Cycle (STLC).
Prime goalThe prime goal is to deliver a reliable and completely functional software product.The prime goal is to check and confirm the software meets the particular requirements and functions appropriately.
Distinct phasesIt comprises stages such as requirements gathering, design, execution, testing, delivery, and maintenance.It comprises stages such as test planning, test design, test implementation, defect reporting & tracking, and test closure.
CoverageIt covers the complete software development process, from start to delivery/ deployment.It covers the complete test process, starting from test planning to test closure.
Core RelationshipSDLC is followed by STLC to validate and verify the software product.STLC is an integral part of SDLC, ensuring the software is thoroughly tested before deployment.
OutcomeThe ultimate outcome of SDLC is delivering a higher-quality product to the customer.The ultimate outcome of STLC is preferably to deliver bug/ flaws-free software. 

When to use SDLC and STLC?

When to Use SDLC:

  1. Software Development: It is used when you wish to design and develop a new software product or app from scratch. SDLC mainly gives a structured approach to the complete development procedure, guaranteeing that all stages, from requirements gathering to delivery/ deployment, are carefully handled.
  2. Major Software Updates: SDLC is appropriate when you are planning to make major or key updates or improvements to the current/ existing software app/ product. SDLC ensures that the alterations are well-planned and implemented, managing the complete stability of the software.
  3. Large-scale Projects: For significant projects with intricate requirements and multiple teams involved, Software Development Life Cycle (SDLC) offers a systematic framework for teamwork, coordination, and collaboration.

When to Use STLC:

  1. Software Tests: STLC is significantly used when you wish to comprehensively test a software product to confirm its reliability and quality. It includes planning, designing, and implementing test cases to detect and report any errors/ flaws.
  2. After Software Development: It is also used after the software development stage to authenticate and verify the product’s functionality. Software Testing Life Cycle (STLC confirms that the software meets the definite requirements and functions appropriately.
  3. Continuous Integration: Software Testing Life Cycle (STLC) is suitable for projects that follow CI (continuous integration) and (CD) continuous deployment practices. It assists ensure that modifications to the software are meticulously tested before being launched.


SDLC and STLC are two separate yet interrelated processes that play a crucial role in developing a new system. Both of these procedures should be carefully considered and executed to ensure the successful and efficient development of superior-quality software products

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Frequently Asked Questions (FAQs)

  • Is STLC a part of SDLC?
    Yes, Software Testing Life Cycle (STLC) is a subset of Software Development Life Cycle (SDLC). Whilst SDLC covers the complete software development process, STLC precisely focuses on the test phase. Hence, STLC is a crucial component of SDLC.
  • What is V-Model SDLC?
    The V-Model is a form of SDLC model, demonstrating the Verification & Validation model. In this approach, the implementation of procedures occurs sequentially, forming a V-shaped life cycle.
  • How is STLC related to SDLC?
    SDLC (Software Development Life Cycle) and STLC (Software Testing Life Cycle) are closely intertwined as STLC is a crucial element of the entire software development process. STLC operates as a subset of SDLC (Software Development Life Cycle), particularly focusing on testing actions to guarantee the dependability and overall quality of the software product under development.
  • How do SDLC and STLC impact the software development timeline?
    SDLC and STLC can impact the software development timeline by confirming a systematic and effectual approach to development and testing. When both are followed appropriately, it helps in delivering top-quality software within the proposed schedule.
  • Do SDLC and STLC share similarities with Agile?
    Agile stands apart from STLC and SDLC owing to its emphasis on adaptable and flexible software development practices. In contrast, old SDLC models like the waterfall model are based on a predictive approach, with sequential and predefined steps.
  • Can SDLC and STLC be used independently?
    No, SDLC and STLC are interrelated and must be used together for effectual software development. SDLC sets the foundation for the complete development procedure; on the flip side, STLC validates and confirms the functionality of the specific software.
  • How can the collaboration between development and QA teams be enhanced during SDLC and STLC?
    To enhance collaboration, development and QQA teams must have open communication channels, share project documentation, participate in frequent meetings, and work together to know requirements and address problems proactively.
  • What are some common challenges in executing SDLC and STLC?
    Some common challenges count managing project timelines, addressing changing requirements, guaranteeing effective communication between teams, and managing a balance between developments and test efforts.
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