Functional testing is a sort of testing that aims to determine whether each application feature functions in accordance with the program requirements. The result of each function is compared to the relevant requirement to see if it meets the end user's expectations.
Functional testing is a quality assurance technique and a sort of black-box testing that bases its test cases on the software component under test's specifications. The internal program structure is rarely examined when testing functions by feeding them input and reviewing the result.
Behavioral testing is another name for black box testing. The core structure, design, and implementation are unknown to the tester during this testing. Functional testing is a sort of testing. This sort of testing is known as black-box testing since the tester cannot see the internal code.