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A Helpful Guide for What it Takes to Perform Thorough Functional Testing

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Functional testing services represent a form of black box testing that validates that software works as expected. Specifically, it is a form of testing undertaken from a user perspective that evaluates each feature against a set of acceptance criteria. The results are categorized as either “passed” or “failed” based on that criteria. Developers modify the code to fix the failed feature. After the developer implements their code changes, the test technician reruns the test to ensure nothing else was affected by the changes made to fix the initial issue. The cycle continues until the product meets predefined acceptance criteria.  

There are many forms of validation that fall under the umbrella of functional testing services. Each of which validates a specific area of the system. Teams typically employ most of the common types which include usability, interface, and regression testing. Keep reading for details on what it takes to perform thorough functional testing for your software systems.   

What is Functional Testing?

Functional testing services refer to the work required to validate that software works as expected.   

A test begins when a test technician inputs data into the system to evaluate a specific function. The test technician assesses the results to determine if it provides the expected outcome based on a set of acceptance criteria. The test technician then determines if the feature passes or fails based on that criteria and documents the defective feature test condition to communicate and reproduce the observed failure. The developers then modify the code to fix the defect that caused the failure. Functional testing continues in a loop of test, fix, retest until the product meets a standard that is acceptable to the team. At the end of functional testing, the project team decides to either deploy to production or continue adding new features and fixing defects, starting the functional test cycle again.    

It is important to note that functional testing is a form of black box testing in that the test technicians have no knowledge of the internal workings of the system. Thus, the focus of black box testing is on validating the system from the perspective of a user. As such, it helps to ensure that the QA team’s evaluation of a feature is based on how the system behaves under real-life scenarios.  

The Value of Functional Testing

Functional testing services help companies gain a competitive edge. Today’s competitive marketplace is flooded with companies offering such similar products that it is easy to get lost in the shuffle. When that happens, companies miss opportunities to land new customers, increase their market share and expand their brand. So, what can companies do to set themselves apart? Many are leveraging technology as their competitive edge and brand differentiator. With that said, a company’s technology must be impressive, intuitive, reliable, and provide such an outstanding experience that customers can’t help coming back for more. More simply stated, the customer experience must be flawless.   

According to a study sponsored by IBM, data breaches cost companies an average of nearly $3.9 million dollars each year. Often, these breaches stem from minor glitches that could have been avoided with proper testing. Functional testing services performed by the QA team evaluate every area of the software under a variety of scenarios and data input. The goal is to have enough test coverage to catch not only the major issues but also the small things that might get overlooked.  

Many companies are bound by compliance and regulatory requirements such as privacy, information storage, and information reporting. When a company’s software doesn’t work correctly, they run the risk of violating their regulatory obligations. The resulting fines and legal action could wreak havoc on a company’s finances not to mention their reputation. Functional testing services help companies validate that their systems are compliant and help them avoid the consequences of not doing so.   

Three Goals of Functional Testing

  1. Your software works as expected. Functional testing verifies that the application or software being tested meets the defined functional requirements and specifications. This helps ensure that everything functions as expected (thus the name functional testing!).
  2. You save your company money. Implementing a functional testing strategy can help prevent costly defects. In fact, studies from the National Institute of Standards and Technology suggest that software failures cost the US economy close to $60 Billion annually!
  3. Happy customers will increase your profits. Functional testing enhances user satisfaction by testing basic usability, mainline functions, accessibility, and proper error messaging, ultimately delivering a high-quality product that aligns with user needs.

The Basics of a Functional Testing Strategy

There are two basic approaches to a functional testing service strategy. Requirements-focused software testing determines the priority and order of testing efforts based on a prioritization of the user requirements as defined in the functional specification. Thus, the requirements document forms the basis for the acceptance criteria. Business-process-focused testing is a form of role-based testing that determines the validation priority based on how the system is used in the context of use cases. Given that, business-process-focused testing relies on the QA team working alongside the Subject Matter Experts (SMEs) to determine the acceptance criteria.   

Each approach has pros and cons that must be weighed against the context of the nature and complexity of the system. Requirements-focused testing works well for complex systems where there is a well-documented and approved requirements specification. Due to the complexity of the system involved, having a requirements specification as the basis for testing efforts helps ensure the proper coverage to meet those requirements. Business-process-focused evaluation is ideal for systems heavy in process or use cases. Validating process-heavy systems often requires a level of domain knowledge that can only be achieved by working alongside the SMEs. 

Functional testing services revolve around a multi-step process. The initial step is to identify the functions under test. As mentioned, those functions are determined by either the functional specification or the SMEs. Given the list of features, the team must then define the data input required for each feature. The team must also determine the expected output from those tests. Once input and output have been determined, the QA team executes those tests either manually or, in some cases, using automated tools. After each test, the test technician compares the results to the expected output and makes a pass/fail determination.   

Both functional and non-functional testing should play crucial roles in shaping a testing strategy. Although our primary focus in this article is functional testing, it’s essential to briefly distinguish between the two. In essence, non-functional testing examines application attributes that, while not directly tied to the product’s core functionality, may influence the overall user experience. By evaluating the experiential quality, non-functional testing can often uncover more significant system issues. Examples of non-functional tests include performance, usability, and load testing. On the other hand, functional testing is an umbrella term covering various test types, each targeting a specific function, as outlined below.

Types of Functional Testing

No single test method is enough to fully test the system. It is important for project teams to use multiple methods throughout the testing cycle. Many of these methods are repeated as often as necessary until the system meets the required standards.    

User Acceptance Testing  

User Acceptance Testing (UAT) is a crucial phase of the software testing process that focuses on validating whether a software application meets the needs and requirements of its end users. As a type of functional testing, UAT ensures that the software works as intended and delivers the expected functionality in real-world scenarios. This is important because it directly impacts the overall user experience, which is a key determinant of the success of any software product.

Another factor to consider in UAT is digital accessibility testing. Digital accessibility testing plays a critical role in user accessibility testing as it ensures that software applications are inclusive and consider the needs of users with varying abilities. By involving assistive technology users in the manual testing process, developers can gain a deeper understanding of the unique challenges faced by individuals with different abilities, such as visual or hearing impairments, learning, or cognitive limitations. This enables developers to make valuable adjustments to improve the overall usability and accessibility of the software.

Unit Testing  

Unit testing is a specific functional testing service that focuses on evaluating the code to determine if it functions properly. This type of validation evaluates the smallest piece of code that can be isolated and assessed individually. That unit of code could be a method, a line of code in a method, or a property. The benefit of unit tests is that by isolating components of the code, there is less risk of code coupling. A good unit test should have no dependencies on outside factors such as a database or file system. They should be repeatable in that the test should return the same results under the same conditions with each execution. Lastly, they should be self-checking by automatically determining pass/fail status without human interaction.   

Integration Testing  

While unit testing meticulously examines individual software components in isolation, integration testing takes the baton, ensuring these components harmonize when brought together. In essence, it validates seamless collaboration between different modules and systems.

Integration testing shines a light on potential defects lurking within the integrated components of the software under test. Its core objective is to expose any glitches in these interactions, guaranteeing that components function cohesively as intended.

System Integration Testing (SIT) expands the scope of integration testing by incorporating multiple components or even entire systems. This can encompass diverse software and hardware combinations. Imagine testing a banking application – integration testing would verify the smooth execution of transactions across various modules, from establishing a savings account to transferring funds.

Interface Testing  

Software systems often interface with other software systems to provide user functionality. This connection is called an interface. QA teams must validate that the links to other systems operate as expected. An example of an interface is a web service API call to a third-party API to retrieve pricing information. Test technicians can validate this functionality by inputting the required information, performing the function that makes the API call, then validating the results.   

Regression Testing  

Regression testing is a form of software testing that ensures the system still works properly after code changes. Test technicians rerun either a subset of the test suite or the full test suite. There are typically two types of regression tests, smoke testing and sanity testing as discussed below.   

Smoke Testing  

The QA team requires some level of measurement to determine if the system works well enough to proceed with further validation efforts. It is a non-comprehensive and high-level type of evaluation that covers the major components of the system. The idea isn’t to determine if the system works perfectly. The goal, however, is to determine if the team can proceed with further validation efforts despite the existing defects.   

Sanity Testing  

Like smoke testing, sanity testing is also a non-comprehensive and high-level evaluation of the software. However, it is performed after code changes. The goal of sanity testing is to verify if the system continues to work as expected given the changes introduced into the system.  

Functional Testing Services Best Practices

Adhering to a set of standard procedures gives the team a clear roadmap for the test cycle. This roadmap should help the team navigate priority, traceability, and communication. Not only that, these functional test services best practices help avoid some of the common traps that hinder the process.  


An effective strategy is one that covers as many scenarios as possible. However, determining where to start is a decision that can mean the difference between a successful cycle and a frustrating turn of events that seems to lead nowhere. Before testing begins, it is crucial to prioritize the functions in question. That way, the team can start their validation on items with the highest significance in terms of user importance, risk, and cost-benefit. Beginning with the high-priority items allows the team to address them earlier in the evaluation cycle rather than rushing at the end to “fit it in” before deployment.  


Before testing efforts begin, it is important to develop a matrix that maps the relationship between requirements to test cases. With a traceability matrix, the team can quickly identify that all requirements have been addressed. It is also essential for the team to manage traceability through requirements changes, as these changes could impact the outcome of existing tests. Requirements changes could also require new test cases that must be developed. Traceability is ultimately critical to ensuring proper system coverage.   


A formal feedback loop should be established at the onset of testing. The team should document expectations for how new defects are to be reported. Additionally, the team should document how the developers will communicate releases to the test technicians for re-validation. Lastly, there must be a formal process for closing defects that ensures all parties agree on the item in question.   

Validation of Test Cases 

As the size and complexity of the system increase, so does the risk of redundant scenarios. Given that, the project team should have a clear process for evaluating each new case, to ensure it is not a duplicate. System complexity also increases the risk of logic errors. The test technician should work closely with the requirements analysts and the SMEs throughout the process so that logic errors can be spotted by those with enough domain knowledge to do so.  

It is important for project teams to employ a variety of functional testing services to ensure proper coverage. By doing so, they minimize the risk of bugs that cost the company customers, money and damage their reputation.   

QualityLogic’s team of experts has over 30 years of experience providing functional testing services in a variety of development methodologies. We use industry-proven tools and techniques to give each feature the level of examination required to ensure a positive user experience across the system. Learn how QualityLogic’s functional testing services can help detect defects early so you can deliver a product that far exceeds your customer’s expectations.  

Manual vs. Automated Functional Testing: Striking the Right Balance

Manual testing involves a human tester executing each step, replicating real-world user interactions. This approach excels at uncovering usability and user interface issues. Beginners can learn manual testing techniques more easily, and it doesn’t require programming knowledge (particularly in black-box testing). However, manual testing is time-consuming and requires significant human resources.

Automated testing, on the other hand, leverages tools and scripts within frameworks to run tests without human intervention. This proves highly efficient, especially for executing numerous complex test scenarios under tight deadlines. Automated tests run quickly, integrate seamlessly with development processes, and provide broader test coverage. Additionally, they offer precise diagnostics and valuable insights from test data. However, the initial setup costs for automation can be high, and automated tests might miss issues a human tester would readily identify.

The ideal approach to functional testing often involves a strategic blend of both methods. Manual testing excels at tasks requiring human judgment, while automation tackles repetitive tasks and ensures thorough coverage.

Need functional testing?


Gary James, President/CEO

Over the last 35+ years, Gary James, the co-founder and president/CEO of QualityLogic, has built QualityLogic into one of the leading providers of software testing, digital accessibility solutions, QA consulting and training, and smart energy testing.

Gary began his QA journey as an engineer in the 1970s, eventually becoming the director of QA in charge of systems and strategies across the international organization. That trajectory provided the deep knowledge of quality and process development that has served as a critical foundation for building QualityLogic into one of the best software testing companies in the world.

In addition to leading the company’s growth, Gary shares his extensive expertise in Quality Assurance, Software Testing, Digital Accessibility, and Leadership through various content channels. He regularly contributes to blogs, hosts webinars, writes articles, and more on the QualityLogic platforms.