Software testing is

Answer: the process of executing a program with the intent of finding errors.

Explanation:

• Primary purpose: Testing is primarily aimed at detecting defects by executing the software and observing failures when actual behavior deviates from expected behavior.

• Testing cannot prove the absence of defects: While tests can reveal the presence of defects, they cannot guarantee that no defects exist unless every possible input and state is tested, which is generally impossible.

• Testing builds confidence and provides evidence: Although testing increases confidence that the software behaves correctly for the tested scenarios, this is a byproduct; the defining intent is to find errors.

Why the other phrasings are not the best single-sentence definition:

• "the process of establishing that errors are not present." — This claims a proof of no errors, which testing cannot provide in practice.

• "the process of establishing confidence that a program does what it is supposed to do." — This is true as an outcome of testing, but it omits the central intent to discover defects.

• "the process of executing a program to show that it is working as per specifications." — Executing to show conformance describes verification activities for specific cases, but does not emphasize the tester's intent to expose deviations and failures.

Summary:

• The most precise concise definition is that testing executes software with the intent of finding errors; other descriptions capture aspects (like building confidence or verifying specifications) but are incomplete on their own.