What is functional testing?

Functional testing is a type of testing that verifies whether the software conforms to specified functional requirements and specifications, without considering the internal structure of the system (a "black box" approach). It aims to check that each software function operates as expected by users.

Main objectives of functional testing:

• Verification of functions against requirements.
• Guarantee of correct operation of all intended functions.
• Detection of defects related to incorrect implementation of functions.

Types of functional testing:

• Unit Testing: Testing individual components or modules. Usually performed by developers.
• Integration Testing: Checking the interaction between modules or systems.
• System Testing: Comprehensive testing of the entire system to verify compliance with overall requirements.
• Acceptance Testing: Final testing conducted by the customer or end-user representatives to confirm the product's readiness for release.
  • Alpha Testing: Acceptance testing performed by an internal team close to developers.
  • Beta Testing: Acceptance testing conducted by real users in real conditions.

The process of functional testing includes:

1. Requirements analysis.
2. Test planning.
3. Development of test cases.
4. Preparation of test data.
5. Execution of test cases.
6. Results analysis and defect registration.
7. Re-testing after defect fixes.

Examples of test cases for functional testing of a web application:

Steps	Expected Result
1. Open the login page. <br> 2. Enter correct login and password. <br> 3. Click the "Login" button.	User is successfully authenticated and redirected to the main page.
1. Open the registration page. <br> 2. Leave the "Email" field empty. <br> 3. Click the "Register" button.	Validation error message for the "Email" field appears.

Functional testing is a fundamental and mandatory stage of quality assurance for software.