Software testing is the process by which a software product or application is evaluated to ensure that it matches expected requirements and functions without any defects, errors, or bugs. It may be done through manual or automated tools, and its benefits include the early prevention of bugs, reduced development costs, improved performance, and fixing of any gaps with respect to expected requirements and actual performance. Companies that invest in software testing set themselves up to save millions of dollars per year; their software is delivered with fewer errors, ensuring customer satisfaction and leading to improved sales and profit.

There are several types of software testing, each with specific strategies and outcomes:

1. Functional testing: Functional testing is a type of software testing that ensures each function of the software application works as intended. It can be performed manually or via automation. It may involve testing application functionalities (e.g. logging in or checking out online), or testing the flow of the GUI screen to ensure that user navigation works fine throughout the application.

This is done by first understanding functional requirements, identifying test input data towards these requirements, defining expected outcomes to this test input data, executing test cases, and then comparing actual and expected outcomes.

Functional testing, therefore, ensures a stable user interface with optimum functionality and accessibility, while meeting business requirements.

2. Unit testing: Unit testing is performed by isolating a small section of code (Eg: a function or a method) and validating it for correctness. In this manner, individual units or components of the software are tested for their functionality. It is the first level of software testing done before the code is integrated, and is usually performed by developers.

Unit testing can be performed either manually or through an automated tool, though most developers and QAs prefer to use automation. Unit tests are executed by developers by writing code to test a specific function of the application in isolation.

While it may be time-consuming and resource-intensive, unit testing ensures that developers can catch and identify bugs early on in the development process, refine their code, and ensure that all modules work as intended, thereby improving overall product quality and reducing time spent on later, more costly fixes.

3. Integration testing: Integration testing is the second phase of software testing that follows unit testing. Here, individual software units or components are tested as a whole for functionality. This ensures that no bugs creep in when individual units are integrated.

The process of integration testing involves identifying relevant modules that need testing once integrated, defining test cases for the interaction between these modules, and deciding test input data for this test case execution, following which any bugs can be reported and fixed.

Integration testing is then done via an incremental approach where modules are added in their logical sequence and then tested for correctness. It can also be done in a non-incremental fashion in cases where the modules are interconnected in a more complex manner. Here, the modules are tested against other existing modules in a ‘big bang’ method.

In this manner, integration testing ensures that all software modules work cohesively and helps fix integration issues early on in the Software Development Life Cycle (SDLC).

4. Exploratory testing: Exploratory testing involves creating test cases based on ‘what-if’ scenarios, where testers do not check the system in advance, but through the lens of learning and discovery, explore possible scenarios that require deep-dive testing. This type of software testing is subjective in nature and depends on the individual tester’s objectives, wherein they will explore the application in several different ways, study its flow, and simultaneously undertake both test design and execution.

Unlike the scripted testing approach that arises from requirements and can in most cases be automated, exploratory testing is more complex and spontaneous in nature, involving the human element of learning and adapting. Exploratory testing may be performed free-style which follows no stringent rules, strategy-based which calls for a particular testing methodology, or on the basis of scenarios such as real use case scenarios.

Its pros include its investigative approach that helps find bugs that may otherwise go undetected and deeper test drill-down than other testing techniques. However, its cons include the fact that it is heavily dependent on the individual tester’s skills and domain knowledge.

5. Regression testing: Regression testing is performed at any point when developers change or modify the code. This is done to ensure that the new modification or feature does not break the application’s functionality or introduce new bugs into the system. It may also be done when a new feature is added or when a functional defect has been fixed.

This type of testing can be done manually, but, owing to its time-consuming nature, can be automated using a test automation tool for better results. Once the bugs have been identified and fixed, either all tests or a selection of tests may be re-executed as part of the regression testing process to ensure that existing functionalities have not been adversely impacted. Alternatively, test cases may be prioritized based on business impact, and only these tests are re-executed.

While regression testing is required every time a small modification or change is introduced, it does help enhance the product’s overall quality and ensures that issues once fixed, do not reoccur.

6. Stress testing: Stress testing or endurance testing is a type of performance testing that is used to ensure that an application is robust, secure, and capable of handling extreme workloads while providing effective error handling in the case of system failure. It is also a means to check if the system is capable of saving data during a crash.

Here, the application is made to endure extreme conditions for a regulated period of time until it causes a crash. In this manner, the application’s limit of withstanding ‘stress’ can be evaluated while also ensuring that the system is capable of recovering from failure. For example, consider the spike in activity on an e-commerce website during its Black Friday sale. Stress testing helps ensure that the website is capable of handling such a spike, protecting the business from potential loss of revenue and customer loyalty.

While stress testing involves testing the application under extreme conditions until it fails, load testing tests its behavior under normal conditions or expected workload. ‍

7. Acceptance testing: Acceptance testing is the process of verifying that the entire system works as expected. It is usually performed by the end user or client to verify that the software product works as intended before they pay for it and it moves to production.

This is the last stage of software testing that occurs after unit and integration testing. It helps to identify defects that may have been missed during earlier stages of testing and is a great way of ensuring that feedback on product performance and end-user satisfaction is acted upon.

As the tester in this case has good knowledge of the business, this type of software testing provides ample clarity on the product’s actual capabilities, while ensuring that it fulfills all requirements from both business and technical standpoints.

In this guide, we have explored some of the most prominent types of software testing. Using a well-defined test management framework, even the most complex of applications can be tested using the most optimal software testing method. Just as essential as validating base requirements is ensuring testing effectiveness: running the least number of tests to identify the largest number of defects.

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