1. Introduction to Software Testing
The concept of test levels in software development is fundamental to creating a robust and effective testing strategy. Test levels refer to the different stages at which various types of tests are performed during the software development lifecycle (SDLC). Each level targets a specific layer of the software, focusing on distinct objectives and employing different test methods. This hierarchical arrangement of testing ensures that every aspect of the software, from individual components to the entire system, is thoroughly verified (Read more about the testing pyramid).
The necessity of different test levels stems from the layered and complex nature of software systems. Software development is not a linear process; it involves multiple stages, each with its own set of requirements and challenges (Testing Structure: Classifying Tests at Different Levels).
Testing levels refer to the different stages or phases of the software development life cycle (SDLC) at which testing activities are performed. Each testing level has its specific objectives, scope, and focus. The primary testing levels include:
Unit Testing.
Unit testing is done at the code level, where each component is tested individually to ensure their impartiality and analyze their functionality. Automating unit tests is possible and highly recommended in today’s fast-paced development environment. To make a unit test, you should outline what you expect the code to do and write the code, which will check if it is doing what you expect. You should then run the unit test to verify that everything works as expected. For example, let’s say you have a calculator program that adds two numbers together. You can create a unit test that verifies the numerical values that the calculator program returns are correct. You could also create tests that verify edge cases and errors are handled correctly.
- Objective: To verify the smallest units of code (individual functions, methods, or modules) to ensure they function as intended.
- Scope: Isolated testing of each unit in isolation.
- Tools: Often automated testing tools are used.
- Responsibility: Typically the responsibility of developers.
Integration Testing.
Integration testing basically tests the interfaces between different components. In unit testing, the independent units or entities developed by the developers get tested in integration testing. Those entities are integrated and interfaces between those components have been tested in integration testing. Integration testing can be done between 2 complex modules or between multiple modules. There are a lot more ways to do integration testing. The core idea of integration testing is to test the interface when you integrate these smaller units into bigger chunks (Software Test Levels).
- Objective: To verify the interactions between integrated components or systems.
- Scope: Testing the connections between units/modules and their combined functionality.
- Tools: May involve both manual and automated testing.
- Responsibility: Shared between developers and testers.
System Testing.
System testing is the third level of the test. It is where the quality assurance personnel test the system’s compliance. It ensures that the system meets the demands. This testing occurs in a very similar environment to the production environment.
- Objective: To validate the complete and integrated software system as a whole.
- Scope: Testing the entire system against specified requirements.
- Tools: Can involve both manual and automated testing tools.
- Responsibility: Mainly the responsibility of dedicated testing teams.
Acceptance Testing.
In acceptance testing, test cases use real-world business scenarios. They do this to test the software used by clients, businesses, or customers. When all the features and functionalities work, the client will accept the software. It is the final testing stage before the program goes out for use. Another name for this is user acceptance testing (UAT).
- Objective: To ensure that the software meets the user's expectations and requirements.
- Scope: Validating the system from the user's perspective.
- Tools: Usually involves manual testing.
- Responsibility: Involves end-users, product owners, or client representatives (Levels of Software Testing: A Definitive Guide).
Alpha Testing.
Alpha testing falls under the category of Acceptance Testing. Some unit or smoke tests of features may have been performed during the development of the software, however it is important to Alpha test the overall completed product in order to catch all possible issues and give the developers a chance to address them before real user tests are carried out.
Alpha testing is done by internal developer and QA teams, with its main goal being to ensure that the software is functional, reliable, and free of any defects or errors. Alpha testing generally attempts to simulate real user behavior by using black and white box testing techniques.
- Objective: Conducted as an initial phase of acceptance testing, often by internal teams.
- Scope: Identifying major issues before releasing the software to a larger audience.
- Tools: Manual testing tools are typically used.
- Responsibility: Internal testing teams or a selected group of users (What is Alpha Testing?).
Beta Testing.
Beta testing is essential as the next step in the software testing procedure following alpha testing and only before the final release. A software product enters beta testing after the initial alpha testing phase and before the final release.
It entails letting a small number of external testers or end-users use the software in real-world circumstances and provide comments.
- Objective: Conducted by a selected group of external users before the software's official release.
- Scope: Collecting feedback from real users to identify any remaining issues.
- Tools: Manual testing tools are commonly used.
- Responsibility: External users, often not part of the development team.
Types of Beta Testing:
- Open beta testing
- Closed beta testing
- Selective beta testing
This method is all about delivering the software to an external testing or end-user group, having them put it through its paces in real-world circumstances, and providing feedback. The primary goal of beta testing is to collect useful information regarding the software’s ease of use, functionality, compatibility, and general user interface before its final release.
Its characteristics are:
- Real-World Environment
- Feedback-Driven Testing
- External Testers
- Limited Duration
- Emphasis on Usability & User Experience
- Iterative Procedure (Difference between Alpha and Beta Testing).
User Acceptance Testing (UAT).
User Acceptance Testing is a testing methodology where clients/end users participate in product testing to validate the product against their requirements. It is done at the client’s site on the developer’s site. For industries such as medicine or aerospace, contractual and regulatory compliance testing, and operational acceptance tests are also performed as part of user acceptance tests. UAT is context-dependent and UAT plans are prepared based on requirements and are not required to perform all kinds of user acceptance tests and are even coordinated and contributed by the testing team (User Acceptance Testing (UAT) – Software Testing).
- Objective: To ensure that the software meets the user's business requirements.
- Scope: Confirm that the system is ready for production use.
- Tools: Primarily manual testing.
- Responsibility: End-users, product owners, or business stakeholders.
These testing levels are organized in a hierarchical manner, with each level building on the results of the previous ones. The goal is to progressively validate the software and ensure its reliability and quality at different stages of development (Read more about the testing pyramid).
Useful links:
“SOFTWARE TESTING. BASE COURSE” By Svyatoslav Kulikov
A Practitioner's Guide to Software Test Design
“TESTING DOT COM, OR MANUAL ON HARSH TREATMENT OF BUGS IN INTERNET START-UPS” By Roman Savin
“BLACK-BOX TESTING: TECHNIQUES FOR FUNCTIONAL TESTING OF SOFTWARE AND SYSTEMS” BY BORIS BEIZER
ISTQB Certified Tester Foundation Level: A Self-Study Guide Syllabus v4.0
ISTQB Foundation Level exam (CTFL) in 2023
Foundations of Software Testing: ISTQB Certification by Dorothy Graham