Software testing and debugging — Technology, 14–17 years
How programmers find mistakes and check that a program behaves as intended. Technology, 14–17 years.
A program needs checking
A program can run without crashing and still give the wrong answer. Testing means trying planned examples, including awkward ones, and comparing the result with what should happen. Debugging is the detective work of finding the cause of a failure and changing the code so it is fixed.
Why test at all?
People write instructions, but people also misunderstand requirements and overlook unusual cases. A small mistake in a payment, timetable or medical system can affect many users. Testing does not prove that every possible input is safe; it gives evidence, early, that important behaviours work and shows where to investigate.
A boundary case
Suppose a program gives free delivery when an order costs at least €30. First, test €20: paid delivery is expected. Next, test €30: free delivery is expected. Finally, test €30.01 and €29.99. If €30 is charged for delivery, the comparison sign or the rule has been coded incorrectly.
The happy path is not enough
A reasonable mistake is to test only the normal route: a valid password, a full basket and a strong internet connection. It feels convincing because that is how we expect to use the app. But failures often hide in empty fields, very large numbers, repeated clicks or lost connections, so those cases deserve deliberate tests too.
Where it appears
Testing is used for games, websites, public-transport apps, banking and equipment such as aircraft controls. A team may run automatic tests whenever code changes, then ask people to try the product in realistic ways. The checks reduce risk, but they do not replace careful design or responsibility.
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