Software Testing Methodologies and Levels Of Testing

We’ll explore what it truly means to be a tester from understanding their core responsibilities to unpacking key testing methods, fundamental principles, and the different levels of testing involved. While software testing can be performed manually or through automation, our focus here will remain entirely on manual testing to help you build a strong foundation before stepping into automation. In this article we will discuss about “Software Testing Methodologies and Levels of Testing”

Manual Testing

The tester personally executes test cases without using any automation tools. The development team aims to uncover bugs, issues, or defects in the software application.. As the most fundamental approach to testing, manual testing plays a crucial role in identifying critical flaws and ensuring the software functions as expected.

Before automating any test cases, QA teams must manually test the new application to ensure it’s stable and functional. While manual testing requires more time and effort, it lays the foundation for successful automation by helping testers evaluate what’s worth automating. The beauty of manual testing is that it doesn’t require knowledge of any specific tools—just a strong understanding of testing principles. One of the core truths in software testing is: “100% automation is not achievable.” That’s exactly why manual testing remains an essential and irreplaceable part of the QA process.

Roles and Responsibilities of a Tester

1) Read and Understand Project Documents: Testers begin every project by verifying the documentation. Their first responsibility is to carefully review all project-related documents. If they come across any unclear or confusing points, they raise questions during the daily scrum calls to ensure clarity and alignment from the start.

2) Create the test plans, and test cases based on the requirements: After reviewing the project documentation and finalizing the user stories, testers start writing test cases and test scenarios based on those user stories or defined requirements. This step ensures complete test coverage and aligns testing efforts with the business needs.

3) Review and baseline the plan/test cases with the lead: After completing the test scripts, the tester reviews them with the business team to ensure accuracy and alignment with requirements. Once everything is validated, the tester obtains formal sign-off to proceed with execution.

4) Setup Environment: Testers begin by setting up the testing environment, which includes verifying test user credentials and ensuring they can access the system as required. Next, they check the environment externally to make sure nothing is broken or unstable. Once everything looks good, they move forward with executing the test scenarios confidently.

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5) Execute Test Cases: After setting up the environment, the tester begins executing the test scripts to validate the application’s functionality and ensure everything works as expected.

6) Report the Bugs: When testers don’t encounter any bugs during testing, they close the user story or test script by attaching test evidence—such as screenshots or screen recordings—for reference. However, if they do find a bug, they promptly raise a defect in the tracking system and tag the developer to ensure the issue is addressed quickly.

7) Retest of Bug: After the developer fixes the bug and updates its status to “Fixed,” the assigned tester retests the software to verify the resolution. If everything works as expected, the tester closes the bug and marks it as resolved in the tracking system.

Two testing methods that testers must follow

1) Static Testing: Testers examine the software for errors without actually executing the code. This early-phase testing helps identify defects right from the development stage, making them easier and more cost-effective to fix. Static testing also uncovers issues that dynamic testing might overlook.

Testers primarily use two methods during static testing:

• Manual Inspections: They manually review code, design documents, or requirement files to catch deviations. This process includes activities like walkthroughs and peer reviews.
• Automated Static Analysis: Tools automatically scan the code to detect potential issues like syntax errors, security vulnerabilities, and coding standard violations.

In short, testers carefully verify project documents and files to ensure everything aligns with the requirements. This process commonly known as verification confirms that the product is being built correctly, before any code is run.

In static testing, teams perform verification activities like reviews, inspections, walkthroughs, static analysis, and document validation. By catching flaws early, it strengthens the foundation for successful software delivery.

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2) Dynamic Testing: Testers evaluate the software’s behavior during execution by performing dynamic testing.This type of testing focuses on the actual running code—analyzing how the system responds to varying inputs and whether it produces the expected outputs.

To carry out dynamic testing, testers first build and run the application. They then interact with the software by entering input data and executing specific test cases, either manually or using automation tools. This approach helps identify functional issues, runtime errors, and unexpected behavior in real-world scenarios.

In the Verification and Validation (V&V) framework, dynamic testing supports Validation, which ensures we’re building the right product that meets business and user needs.

Dynamic testing plays a crucial role in quality assurance and includes three main approaches that testers typically follow—each designed to uncover different types of issues during the software lifecycle.

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1) Black Box Testing (Behavioral, I/O testing): In black-box testing, testers focus on validating the software’s functionality based on the given requirements, without looking into the internal code or implementation details. Testers treat the application as a “black box” and actively test its inputs and outputs to ensure it behaves as expected from an end-user’s perspective.

2) White Box Testing (Glass box testing, clear box testing, structural testing): Unlike black-box testing, which focuses purely on functionality, white box testing allows testers to analyze the internal logic, code structure, and data flows within the software.Testers closely examine how the application works behind the scenes, making this approach ideal for identifying hidden bugs and logical errors.

Also known as structural testing, glass box testing, or transparent box testing, white box testing gives testers full access to the source code. With this access, they design detailed test cases that validate the software’s accuracy, performance, and security at the code level.

This method ensures a thorough code-level review, helping teams build more reliable and efficient applications from the inside out.

Note: In mutation testing—also known as code mutation testing, testers intentionally modify small parts of the application’s source code to check whether the existing test suite can detect those changes. These deliberate changes, or “mutants,” simulate common coding errors. When the tests fail as expected, they confirm the effectiveness of the test suite. Mutation testing doesn’t evaluate the quality of the software itself; instead, it measures how well the test cases can catch real-world bugs, ensuring the overall strength and reliability of your testing process.

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3) Grey Box testing: Testers use Gray Box Testing as a hybrid approach that combines the strengths of both Black Box and White Box Testing.In Black Box Testing, testers evaluate the software solely based on its functionality, without accessing or understanding its internal code or structure.In contrast, White Box Testing requires a full understanding of the code and system architecture.

With Gray Box Testing, testers have partial knowledge of the internal workings—just enough to design more informed and effective test cases. They access internal data structures and algorithms when needed, while still validating functionality from an end-user perspective. This balanced approach helps uncover hidden defects and improves both security and performance testing.

Levels of Dynamic Testing

The process of developing software undergoes a number of stages of dynamic testing, including:

1) Unit Testing: Developers perform unit testing to verify that each individual component or “unit” of code functions exactly as intended. These tests typically focus on a single function or feature and are often short, targeted, and easy to automate. By isolating and testing specific pieces of code, unit testing helps catch bugs early and ensures the software behaves reliably from the ground up.

2) Integration Testing: Testers perform integration testing to evaluate how different software modules or components interact with each other. This testing level focuses on checking the data flow and communication between integrated units to ensure they work seamlessly as a whole. By identifying interface defects and interaction issues early, integration testing helps teams deliver a more stable and reliable system.

3) System Testing: System testing allows QA teams to evaluate the entire software application and verify that it meets all defined requirements. At this stage, they thoroughly test the software’s functionality, performance, and usability to confirm that everything works as expected in a real-world environment. This end-to-end testing plays a critical role in identifying issues before the product reaches users.

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4) Acceptance Testing: Testers conduct acceptance testing as the final phase of dynamic testing to confirm that the software is complete, meets business requirements, and is ready for release. During this stage, they evaluate the application’s usability and functionality from the end user’s perspective, ensuring it performs as expected in real-world scenarios.

5) Performance Testing: QA teams conduct performance testing to assess how a software system behaves under specific workloads and real-world stress. They test the system’s speed, scalability, and stability by simulating high user traffic, varying input conditions, and complex scenarios. This helps identify bottlenecks, ensure smooth user experiences, and confirm the software can handle peak usage without breaking down.

6) Security Testing: Testers perform security testing to identify and evaluate potential security vulnerabilities within a software system. They actively assess how well the system’s security measures defend against threats and simulate attacks—like hacking attempts—to observe how the system responds. This process ensures that sensitive data remains protected and that the application can withstand real-world security challenges.

Seven Principles of Software Testing

To achieve the best test results, testers must stay aligned with the planned test strategy without straying off course. But how can you ensure you’re using the right testing approach?

The answer lies in following the fundamental principles of software testing and applying proven web development best practices. These principles serve as a reliable foundation for building effective, efficient, and error-free testing processes.

Every QA professional should know and apply these seven key testing principles, let’s dive in and explore them together.

1) Testing only Proves the presence of defects

Testers actively uncover defects in the software that developers may have missed during the development phase. By identifying these flaws early, they help improve application quality and reduce the risk of failure in later stages.

However, even after developers fix the identified bugs, they can’t guarantee the product will be 100% error-free. Instead, testing helps minimize the number of defects, making the software more stable and reliable. The more issues the testing team finds, the lower the chances of hidden bugs—but testers can never fully prove that an application is entirely free of defects.

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For example, an application might seem bug-free after passing one testing phase, yet hidden issues could still surface in later stages. That’s why continuous testing and validation remain critical throughout the development lifecycle.

2) Exhausting testing is Impossible

Testers quickly realize that testing everything in an application is nearly impossible. The sheer number of possible input and output combinations makes it impractical to examine every scenario from every angle.

No tester or QA team can cover every possibility, which is why no application is ever 100% flawless. While we aim for maximum test coverage and can often achieve up to 99% efficiency, reaching absolute perfection is technically unachievable. Despite the QA team’s best efforts to catch every bug, some defects may remain hidden.

This principle highlights the reality that exhaustive testing isn’t feasible. Instead of trying to test everything, smart teams focus their efforts based on risk and priority, ensuring the most critical features are thoroughly tested where it matters most.

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3) Early testing improves the possibility of fixing defects and saves time, and money as well

QA teams integrate testing early in the development process to significantly improve software quality and reduce costly rework later. The earlier testing begins, the better the results—because catching defects at the start saves both time and money.

Testing doesn’t need to wait until development is complete. In fact, testers can begin validating requirements and feasibility even before a single line of code is written. By reviewing user stories or acceptance criteria, they can identify unclear or unrealistic demands upfront.

Early collaboration between testers and developers also leads to better solutions. Testers can suggest ways to minimize potential failures, while developers, who understand the code deeply, can act on those insights quickly.

When testing starts early, teams catch issues sooner, speed up delivery, and create higher-quality applications that meet user expectations.

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4) Defects tend to cluster

Testers often discover that a single module causes most of the issues within an application. This means one specific part of the system is usually responsible for the majority of errors that lead to failures.

This happens because defects tend to cluster, and flaws are rarely distributed evenly across all modules. In most cases, a small portion of the codebase contains the highest concentration of bugs.

With experience, testers learn to identify these high-risk modules and focus their testing efforts accordingly. However, this approach also comes with limitations. Repeatedly running the same test cases against the same areas can eventually stop uncovering new issues, reducing the effectiveness of your test strategy.

To maintain efficiency, it’s crucial to refresh test cases, reassess priorities, and continuously improve test coverage in areas with historically high defect rates.

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5) The Pesticide Paradox

Testers often face the Pesticide Paradox, where running the same set of test cases repeatedly no longer reveals new bugs. Even if a test initially confirms that the code works correctly, it may eventually fail to detect deeper or newly introduced issues.

This principle encourages testers to use varied testing techniques to uncover different types of defects. To uncover more hidden defects, testers must regularly review and update their test cases. Sticking to the same strategy may make the software appear stable, but it limits the chances of identifying fresh flaws.

To avoid the pesticide effect, testers should introduce new test cases, refine existing ones, and remove outdated tests that no longer add value. By evolving the testing approach continuously, teams can maintain high defect detection rates and ensure long-term software quality.

6) Testing is context dependent

It simply means go with different way of testing with different types of applications.

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7) Absence of error fallacy

Fixing bugs in an application that fails to meet user expectations serves no real purpose. No matter how polished the code is, if the application doesn’t solve the right problem, all the effort goes to waste. That’s why testers must first validate the requirements before diving into test execution.

Even a system that’s 99% bug-free can become unusable if it’s built on the wrong understanding of what the user actually needs. This often happens when teams confuse similarly named requirements or overlook critical context—leading to costly misalignments.

To illustrate this, let’s borrow a story from Hindu mythology:

During the Mahabharata war, Guru Dronacharya was told, “Your son Ashwathama is dead.” Shocked and devastated, he stopped fighting—only to later discover that it wasn’t his son, but an elephant named Ashwathama who had died. This classic mix-up perfectly explains the concept of error fallacy—believing something is correct when it’s based on the wrong assumption.

In software testing, misinterpreting a requirement can lead to flawed test cases and wasted development cycles. Always validate the “what” before testing the “how.”

Types of Software Testing

1) Functional Testing

Testers perform functional testing to verify that every feature in the software works according to the specified requirements. They actively test each function to ensure it behaves exactly as intended, just like running a full health check on the application.

By executing test cases based on user requirements, testers validate that the system responds correctly to different inputs, performs expected actions, and delivers the right outputs. Functional testing helps QA teams catch logic errors, broken features, and mismatches between what’s built and what’s needed—ensuring the software is both reliable and user-ready.

• Unit Testing: Testing which focuses on Individual units or components of a software.
• Integration Testing: Testing the Interface between two software units or module.
• System Testing: QA teams perform system testing by thoroughly evaluating the entire software application to ensure it meets all defined requirements and works as intended. At this stage, they regularly test the software’s functionality, performance, and usability to confirm it delivers a seamless user experience. By simulating real-world usage, testers validate that the system is stable, reliable, and ready for deployment.

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• User Acceptance Testing: Teams perform User Acceptance Testing (UAT) during the final phases of the software development life cycle to ensure the software meets user expectations. After completing all prior testing stages, real end users test the software to confirm it meets business requirements and is ready for launch. That’s why UAT is often called end-user testing—because it validates the product from the user’s point of view before it goes live.
  Note – There are two types of acceptance testing.
  1) Alpha Testing: Testers perform the first end-to-end testing of a product to ensure it meets business requirements and functions correctly. This type of testing is basically performed by the developer itself.
  2) Beta Testing: It is a type of testing where real users test the product in a production environment. The client typically performs this type of testing to verify the software meets their requirements.

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• Sanity Testing: Testers perform sanity testing, a subset of regression testing, immediately after receiving a new software build. They quickly verify that the recent code changes work as expected and haven’t disrupted core functionality. Sanity testing acts as a checkpoint to determine whether the build is stable enough to move forward with more in-depth testing.
• Smoke Testing: Testers use smoke testing to quickly verify whether the core features of a software application are functioning as expected. By running smoke tests early in the development cycle, they can immediately detect and fix critical issues before deeper testing begins.This proactive approach helps QA teams identify major blockers, reduce wasted effort, and ensure that each new build is stable enough for further testing. By confirming that essential functionalities work right from the start, smoke testing plays a key role in improving software quality and accelerating delivery.
• Regression Testing: Every time software engineers update or modify code, they risk introducing unexpected issues. To prevent this, QA teams run regression testing—a process where they re-test previously validated features to ensure new changes haven’t broken anything.By rerunning earlier test scenarios, testers confirm that recent code updates haven’t caused regressions or reintroduced old bugs. Regression testing helps maintain stability, ensures bug fixes remain effective, and verifies that core functionality still works as intended. Many teams also refer to this process as End-to-End Testing, especially when validating the entire application flow after updates.

Retest -> Testing a particular bug after it has been fixed.

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2) Non-Functional Testing

Testers perform non-functional testing to ensure the application meets quality attributes like performance, usability, reliability, scalability, and more. Instead of focusing on what the system does, this testing evaluates how well it performs under various conditions.

QA teams check whether the software behaves according to non-functional specifications and delivers a seamless user experience. While functional testing often takes center stage during daily test cycles, non-functional testing plays a critical role in building stable, efficient, and user-friendly applications.

There are several types of non-functional testing that help assess these key aspects—each contributing to the overall quality and success of the software.

• Performance Testing: In performance testing, testers evaluate the application’s stability, speed, and scalability under various workloads. They measure how the system responds under stress to ensure it performs smoothly, remains stable during peak usage, and can scale effectively as demand increases.
• Memory Testing: Testers check memory storage locations and actively verify that the application doesn’t leak memory during execution. They ensure the system efficiently uses memory resources and releases them properly, preventing performance issues or crashes caused by memory leaks.
• Scalability Testing: Testers perform scalability testing to evaluate how well an application handles increasing or decreasing user loads. This type of load testing measures the system’s ability to scale efficiently as user demand grows, ensuring consistent performance under varying conditions.

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• Compatibility Testing: Testers use compatibility testing to ensure the application runs smoothly across different hardware, operating systems, browsers, network environments, and mobile devices. This technique helps identify issues that may arise due to variations in user setups, ensuring a consistent and reliable user experience across all platforms.
• Reliability Testing: Testers perform reliability testing to ensure the software consistently functions within predefined conditions and timeframes. They operate the system using specific procedures and monitor its behavior under controlled scenarios. If the application fails or crashes during these tests, it doesn’t pass the reliability benchmark. For example, every web page and link should remain stable and accessible any failure signals a lack of dependability.
• Efficiency Testing: Testers conduct efficiency testing to measure how many resources the software system consumes during development and execution. They evaluate whether the application uses memory, CPU, disk space, and bandwidth efficiently, ensuring optimal performance without unnecessary overhead.
• Recovery Testing: Testers perform recovery testing to evaluate how well an application bounces back from crashes, hardware failures, or unexpected interruptions. They intentionally disrupt the system in different ways to observe how quickly and effectively it recovers. Testers use this testing to ensure the software maintains data integrity and restores functionality without losing critical information.

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• Usability Testing: Testers conduct usability testing to verify how easily users can interact with the system, learn its functions, and navigate input and output processes. This testing ensures the software is user-friendly, intuitive, and efficient—delivering a smooth experience that meets real-world expectations.
• Load Testing: Testers perform load testing to evaluate how a system or software application behaves under real-world traffic conditions. By simulating multiple users accessing the application at the same time, they assess how well it handles both average and peak loads.This type of performance testing helps QA teams identify bottlenecks, check system responsiveness, and ensure the application maintains stability and speed—even when demand surges. Load testing plays a vital role in preparing the software for production by confirming it can scale effectively and deliver a seamless experience to all users.
• Stress Testing: Testers perform stress testing to push the software beyond normal operational limits and evaluate how it handles extreme load conditions. This technique helps identify how robust and reliable the system remains when it’s pushed to its breaking point.While stress testing benefits all types of applications, it’s especially critical for mission-critical systems where performance failure isn’t an option. Instead of focusing on typical use cases, testers examine how the system behaves under pressure—emphasizing availability, resilience, and error handling.By simulating heavy traffic, limited resources, or sudden spikes in demand, stress testing uncovers hidden vulnerabilities and ensures the system remains stable and responsive, even in the most challenging environments.

Difference Between Errors/Fault/Failure/Bug/Defects

• Errors: When humans make mistakes during software development or testing, they create errors that lead to a mismatch between the actual outcome and the expected result. These errors introduce flaws in the system that can eventually impact functionality, performance, or user experience.
• Fault: A software product contains a fault when developers implement an incorrect step, method, or data specification during the development process. These faults, if left unresolved, can lead to unexpected behavior or failures in the application.
• Failure: A software system fails when it can’t perform its intended tasks within the required performance standards. According to ISTQB, if the system encounters a fault during execution, it may lead to a component or system-level failure, disrupting functionality and user experience.
• Bug: A software bug causes the system to behave unexpectedly or produce incorrect results. This flaw occurs when the code deviates from the intended functionality, leading to errors that impact performance, usability, or reliability.
• Defects: Testers refer to a malfunction in the software system during testing as a defect. According to the ISTQB, a defect is “a flaw in a component or system that may cause it to fail to perform its required function, such as an incorrect statement or data definition.” These flaws can lead to unexpected behavior, performance issues, or complete system failures if not identified and resolved early.

To summarize: When a developer makes a mistake during coding, we call it an error. If testers discover that mistake during the testing phase, it becomes a defect. Once the defect is reported and needs fixing by the development team, it’s referred to as a bug. And if the software build fails to meet its intended requirements or behaves incorrectly in execution, we classify it as a failure.

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