STLC (Software Testing Life Cycle) - Definition, Phases, Entry & Exit Criteria

Software Testing Life Cycle

Software Testing Life Cycle

Can you imagine a world without technology? Almost impossible, right? We have been so much surrounded by technology and its features that it is terribly difficult to spend even a day without using something related to it.

Numerous companies are constantly developing efficient and useful software to provide us with immense ease in our activities. Now, developing the software is not the ultimate goal. The companies must test all their web products to ensure the best quality and efficiency.

QA tests are as important as they sound. They consist of a number of activities to be performed for the best results at any step. That series of activities performed in a sequence is called the Software Testing Life Cycle (STLC).

If you are developing software and are familiar with Software Development Life Cycle (SDLC), then the life cycle of Software Testing must hold great value in your knowledge and application base.

What Is Software Testing Life Cycle (STLC)?

As we already discussed, STLC is the sequence of activities/processes conducted to test software for ensuring their best performance and quality. It describes a lot of things like entry criteria, exit criteria, goals, objectives, methods, etc. about the tests.

Depending on various parameters, different QA teams can follow different methods but, everyone always looks up to the same objective. Now, let's take a look at the most followed format of STLC

1. Requirements Gathering: Whenever you are going to proceed with an important process that has a number of crucial aspects, you must know all the requirements in order to build a strong foundation for the complex tests.

STLC consists of a long list of activities to perform successful tests. Hence, naturally, it needs us to gather a number of requirements that should be taken care of before everything.

This often includes serious brainstorming sessions with stakeholders to understand what they actually want from the software that is going to get developed.

To clarify in a better manner, let's break it down into some points.

  • The team needs to identify the tests to be performed. It helps to streamline their focus towards a particular direction with maximum efficiency.
  • They have to determine the actual priorities in the tests from the development as well as the business perspective.
  • Preparing Requirement Traceability Matrix (PTM) is an important and effective step.
  • The QA team needs to identify and maintain a suitable test environment.
  • If the necessity is observed, they also need to conduct an Automation feasibility analysis.

Also, the QA team must have backup plans or mitigation strategies for the features that might be developed in the future.

2. Test Planning: We all know how crucial it is to plan every tiny bit of any process. To execute any simple to complex operation, you must proceed with efficient, step-by-step planning.

Similarly, Software tests are also properly planned before the QA team proceeds with the actual steps. The senior QA engineers understand the project and decide the best-suited strategy for the tests.

In this phase, they identify the activities and resources that are necessary to fulfill the test goals and objectives.

Though the planning of the steps and the identification of relevant metrics are mostly done in this phase, sometimes this phase is also merged with the requirement gathering phase.

However, the more strategically broken down the structure is, the more it becomes easier to execute it. The prime activities performed in this phase are -

  • The senior QA engineers prepare the test plan/strategy document for any particular test.
  • They select the necessary tools for the tests.
  • They estimate the test.
  • The risks are analyzed and strategies are built to deal with them.
  • The resources are planned and every team member is given proper responsibilities.
  • The training requirement is decided to achieve the best results.

Despite all theories about merging this phase with the requirement gathering phase, it is a genuinely important phase of STLC.

3. Requirements Analysis: By this phase, the QA team may have found out and decided the requirements of the tests and have made plans accordingly.

But, it is extremely crucial to analyze all those according to the supporting parameters. And, this phase is mostly based on -

  • Requirements document / PRD.
  • Risks associated with the product.
  • Other important test parameters.

This phase can turn out to be really complex as the pseudo test conditions like lurking variables can exempt the QA team from finding out the real/best-suited ones.

Hence, to ensure the maximum level of perfection, the requirements analysis phase should take the following parameters into consideration.

  • How complex the product is.
  • What should be the level of the tests?
  • The risks associated with the product and the overall project.
  • The skillset of the team members.
  • What is the approach towards SDLC?
  • The test conditions must be written in detail to increase the coverage.
  • The exit criteria should be identified to stop the tests at a suitable point.

4. Designing The Tests: After having a clear understanding of everything related to the tests, it's time to design them. This phase itself is a massive task that can be divided into the following sub-tasks.

  • Large test conditions can be broken down into smaller sub-conditions to increase test coverage.
  • The QA team creates requirement traceability metrics and test coverage metrics.
  • The QA team identifies and gains test data.
  • The QA team identifies the required architecture, environment set-up, prepares hardware and software requirement list, and sets up the test environment.

5. Implementing The Tests: Once you have gathered all the required information, planned the tests, analyzed the associated parameters, and designed the test steps, you can now proceed with implementing the actual test steps.

Test implementation can be smoothly done through the following steps -

  • According to the priority of the test cases, the QA team identifies the test cases that will be part of the regression suite.
  • The correctness of the test cases is also analyzed to achieve the best results.

The above is a picture where the involvement of automation is comparatively low. But, with time, tests are becoming drastically automated to achieve better results within lesser time and with fewer resources.

So, let's see what the test implementation phase will look like when the tests are mostly automated.

  • Candidate test cases are identified.
  • The scripts for the test cases are written.
  • The test cases are reviewed.

6. Test Execution: This is one of the final steps where the actual execution of the tests takes place. In this step, the test scripts are run while maintaining the following conditions.

  • The entry criteria are successfully met.
  • The detected bugs are properly reported.
  • On detection of bugs, the software is reverted to the development team for correction and retesting.

The test execution step can be described as the following steps -

  • The tests are executed as per plan.
  • Test results are properly documented and the defects causing failed cases are logged.
  • Defects to test cases are mapped in the Requirement Traceability Matrix (RTM).
  • The defect fixes are retested.
  • The QA team tracks the defects that are causing closure.

7. Conclusion: This phase is all about focusing on the exit criteria of the tests and building reports.

According to the instructions by the senior QA managers and the stakeholders, the test reports are prepared at specific frequencies such as weekly, bi-weekly, or even daily.

As per the expertise of the STLC project managers, they get benefitted from the technical information regarding the defects. However, the non-technical stakeholders are only informed in simple language about how the defects are solved.

8. Test Closure: This is the wrapping-up phase of the long STLC.

The most important activities performed during this phase are checking and grouping test cases based on their status, test completion reporting, collection of test completion matrices & test results, and starting preparation for the future.

This is one of those phases of testing where test team members meet & discuss to analyze testing artifacts and develop better strategies for future test cases. The prime activities involved in this phase are -

  • Cycle completion criteria are evaluated based on time, test coverage, cost, software, critical business objectives, quality, and test metrics are prepared.
  • Test cases are checked and grouped based on their status i.e., executed or mitigated or something else.
  • Whatever is learned during the project is documented.
  • Test closure report is prepared.
  • The customer is provided with the qualitative and quantitative reports of the work product.
  • Test results are analyzed to find out the defect distribution by type and severity.

With the completion of this step, the long STLC is also summed up. The types of tests are differentiated based on the size, scope, and mechanics of the software project that is being developed.

Types of Software Testing

As we saw above, Software Testing is a long process and every step of it is designed according to different requirements for testing different capabilities of a software product or an app.

Let's see the most popular types of testing that solve different purposes.

  • Alpha testing
  • Beta testing
  • Compatibility testing
  • Disaster recovery testing
  • Regression testing
  • Security testing
  • Stress testing
  • Unit testing

However, knowing about so many different types of testing can be really cumbersome. That's why for convenience in identifying the tests, they are divided into three main categories.

1. Functional Testing: The type of software testing that primarily focuses on assessing the functional aspects of a software application, is called Functional Testing.

Here, the QA team mainly emphasizes whether you are getting the expected results or not. The most important examples of Functional Testing are -

These tests can be either manual or automated. The most common and popular tools for this type of testing are JUnit and Selenium.

2. Non-Functional Testing: The testing process that is used to assess the non-functional aspects of a software application, such as reliability and usability, is called non-functional testing.

The objective of this type of testing is to check how well the software application is performing. The types of non-functional testing are -

  • Failover testing
  • Load testing
  • Localization testing
  • Scalability testing

These are mostly done manually.

3. Maintenance Testing: This type of testing is sometimes merged under the name of non-functional testing.

But, the best practice is to keep this type of testing in a separate group. As the name suggests, these tests are all about checking the maintainability of a software product.

In some cases, a few vulnerabilities of a software application are apparent but, most of them are real and can cause severe issues to the software. That's where maintenance testing becomes an important type of testing.


We saw that whatever utilization of any software is, it is extremely important to test it for the best performance and quality. The reputation of your company relies heavily on how beneficial your product turns out to be.

And, with the drastic increase in the number of web products, it has become more essential to automate most QA tests.

Having said that, we must mention that Preflight is the most convenient test automation solution you can get. This simple and extremely efficient browser extension allows you to test complex web applications within a few minutes or even seconds.

To know more about our product, check out our informative documentation. Also, to get abreast with more interesting topics, feel free to check out our blog page.