Software Testing

Software testing is the activity of evaluating a system or its components with the intent of finding whether it satisfies specified requirements and of identifying defects. It is not a phase that happens at the end — it is a discipline that spans the lifecycle: from unit tests written alongside code, through integration and system verification, to acceptance by the stakeholders who will operate or fund the system.

Three ideas drive everything below:

1. Testing shows presence of defects, not their absence. A passing test suite is not proof of correctness; it is evidence that the tested scenarios work as specified. Design tests to find defects, not to achieve a passing run. A suite that only validates the happy path is demonstrating the system works when nothing goes wrong — which is rarely the interesting case.