What Is Functional Testing? (With Types And Steps)

By Indeed Editorial Team

Published April 20, 2022

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Functional testing checks an application or system to make sure it works. Software developers and testers use this detailed testing to check specifications from a list of project requirements. Learning the types and steps allows you to understand, plan, and determine testing sequences and techniques. In this article, we define functional testing, explain its importance, list the different types, and review five steps to test functionality.

What is functional testing?

Functional testing gives developers information about whether an application meets minimum user needs for speed, overall performance, and usability. Testing confirms what needs repair before an application or system is ready for release into a live environment. Testers use a technique called black box that focuses them on validating a system even though they may have little knowledge of the system's logic or code.

Testing involves using test data to identify the inputs, then determining the expected outcome. Next, testers run test cases with correct inputs and compare the results with the project's goals. When the results match the project goals, it's clear that the system or application functions correctly.

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Why is testing important?

These types of tests are important because they ensure you meet the needs of the customer or end-user and produce a defect-free product. They also tell you whether everything works in a secure and safe environment. Tests are also important to:

  • Check basic functions

  • Make it easier for users to operate the system or application

  • Identify and solve problems early

  • Check that users can access various parts of a system

  • Get information to solve future issues

  • Ensure that the system displays correct error messages to users

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Types of testing

Developers decide which tests to use according to the project's functional specifications and business needs. For example, tests may run on a new software system's security that authenticates users or on a company web portal that tracks medical documents for employees. Here are some common types of testing to consider:

Unit testing

The first level of testing, unit testing, involves each unit or an individual component of software, such as a line of code. Developers use a manual or automated unit test to test individual units of an application against the requirements, often reducing the risk of software bugs. A unit test isolates small units in a system so that you can identify and fix them.

Unit testing is often part of the programming phase with programmers who write the production code accessing units to test. During development, a software developer may code criteria in the test to verify that the unit works. The test case execution phase of unit testing logs tests that fail any of the criteria and reports them in a summary.

Smoke testing

Smoke testing checks the stability of a software build, ensuring that important features work. This kind of testing helps developers figure out whether the software is performing as expected and whether it's ready to move into the next phase of testing. Early use of smoke testing before other formal tests finds initial problems and provides more time and resources for future, more rigorous testing stages.

Manual smoking testing involves developers or other testers indirectly performing the smoke tests. Automated testing may save time and money as people program the tests to run automatically. The hybrid testing method combines the best parts of manual and automated testing to check the viability of applications or systems.

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Sanity testing

Often done after smoke testing, sanity testing verifies the major functionality of an application individually and in combination with other elements. This is often a quick and basic test, or set of tests, to determine if a particular application or component is correct. While smoke testing checks for broader functionality, sanity testing determines whether smaller fixes work.

Developers use a sanity test on small code edits and other improvements on a software build. Testing identifies whether these edits work and don't introduce any new problems. This form of testing also ensures the software keeps its functionality.

Regression testing

Regression testing verifies that a recent program or code change doesn't disrupt existing features or trigger instability. A new feature added to a software application, a defect, or a performance issue may also create the need for regression testing.

During this testing, developers repeat a full or partial selection of test cases. The repetitive nature of regression testing means that doing this work manually may be time-consuming. Automating regression testing is common and depends on the volume of test cases and if the tests must be different to check several changes.

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Integration testing

Software development projects often involve many software modules coded by different programmers. Integration tests, which often happen after unit testing, determine if independently developed software modules work when connected to each other. Instead of overall functionality, this form of testing focuses on the data flow and application interface between modules.

Integration testing works well when different teams develop software, checking on whether the product meets the project's goal. Other integrated components also benefit from this testing. For example, you may test a software intermediary, known as an application programming interface, or other third-party applications that allow two applications to talk to each other.

System testing

System testing often happens after integration testing. The system in its entirety undergoes tests to ensure it works and delivers a quality product. Testers at this stage validate the functionality of a system, checking that each user input produces a result they expect.

This testing checks a system from a user's viewpoint and may not require internal knowledge of the design or code structure. Systems testing focuses instead on broad criteria such as security, recovery, and performance. Other areas of focus include the user's interactions with the system and the quality of the documentation, such as any online user manuals or guides.

Beta testing

Beta testing shows developers how people may use the live product. Product teams often give a test version of the product to the user to check its performance. Changes made from feedback at the beta testing stage improve the final version.

Test procedures depend on the project and requirements. For example, beta testing occurs when the product has all the final version features, when it's stable and not susceptible to crashes, and when test participants are users in the workplace.

5 testing steps

Developers use five steps for testing, then refine them depending on the project requirements. Planning the tests begins with detailing the project's needs and ends with a successful product launch. Steps developers use when testing functionality include:

1. Understand user needs

The first step is to identify functions that the application, website, or system needs to perform for your internal or external client. Testing may include the main functionalities, messages, or whether the product is user-friendly. Knowing the needs helps you choose the tests that may provide information to produce the highest functioning product.

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2. Create a test plan

Creating a test plan prepares for different test scenarios you may encounter and guides your actions when these issues occur. For example, your test plan may specify that the quality assurance team passes errors back to the development team before a software release or include an organizational flow diagram to manage defects. Testers also refer to the test plan to guide them on the work process, tools, timelines, responsibilities, and purposes of each test.

3. Create input data

Input data is information a system processes. After you decide which function to test, you create the input data to instruct the system to perform the correct test. You may use previous input data from tests or create new data depending on if you're verifying expected results or testing a system's ability to handle unexpected inputs.

4. Execute test cases

A test case defines what needs validating to make sure a system or application works well and to a high level of quality. Several test cases run after inputting the data to uncover issues and the system's functionality. Recording the results of all tests gives you the opportunity to refer back as you develop solutions and work on future projects.

5. Compare test results

Tests provide evidence about whether the system, software or process works as you expect. This data also allows for comparison with previous test results to check on the success of previous repairs. Save the results of testing and retesting to check the performance and to compare against future test data.

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