Fault base testing technique is

Answer: Mutation testing. Mutation testing is a classic fault-based testing technique.

Fault-based testing overview: design tests specifically to reveal faults by considering likely programmer mistakes.

• Mutation testing process: create many slightly modified versions of the program (mutants) by introducing small faults.

• Run the test suite against each mutant. If a test fails for a mutant, the mutant is "killed"; if it survives, the test suite missed that fault.

• Surviving mutants indicate weaknesses in the tests, guiding improvement of test cases.

Why the other choices are not fault-based techniques:

• Unit testing: a level of testing that checks individual components; it does not by itself define a method of injecting faults to measure test adequacy.

• Beta testing: field testing by real users to find issues in real environments; it is not a systematic fault-injection technique.

• Stress testing: evaluates behavior under extreme load or resource limits; focused on non-functional properties rather than fault-based test design.

Summary: Mutation testing explicitly injects faults (mutations) to evaluate how well tests detect faults, which is the defining approach of fault-based testing.