What is the concept of introducing a small change to the program and having the effects of that change show up in some test?

The concept of introducing a small change to the program and observing the effects of that change in a test is known as "introducing mutations." This approach is commonly used in mutation testing, which is a technique to evaluate the quality of test cases. By deliberately introducing small alterations to the code (mutations), testers can assess whether the existing test suite can detect the changes. If the tests fail when these mutations are applied, it indicates that the tests are effective in identifying discrepancies in the code, providing assurance about the robustness of the test suite. This technique ultimately assists in strengthening the overall testing process by ensuring that tests are not only present but are also effective in identifying defects.