Ultimately, functional testing is AIMED at ensuring that software works as specified and meets user expectations. Functional testing may seem simple on its face, but it involves a variety of methods, some of which may be preferred or PRIORITIZED over others based on the application and organization. These methods are OUTLINED below:

• Unit testing: It involves testing the individual units/blocks of code of the software to validate that they perform as intended.
• Smoke testing: This test only examines the basic functionality of a system to ensure the software works properly (or is not plagued with too many problems) so that the next test can proceed.
• Sanity testing: This type of testing is also known as a build-verification test and is usually PERFORMED after a smoke test. The testing is performed after a complete software build with minor changes is released to verify that the code changes introduced continue to work as intended.
• Integration testing: This test combines individual components/units and tests them together. Tests will ensure that they interact appropriately, as well as reveal any faults between the INTEGRATED units if present.
• Regression testing: This type of testing makes sure that alterations to the code won't affect the system's functionality. The purpose of this test is to ensure that adding fresh code, improvements, or fixing bugs does not cause instability or compromise the software functionality.
• User Acceptance testing: It involves testing software systems from the user's perspective to ensure they meet the requirements. Before software is released to market or production, it must pass the user acceptance test.