Humans are not perfect
Humans are not perfect, and since we are the ones doing the programming, a lot of times programs have what´s known as bugs, or errors(Fun Fact: they are called bugs because way back in times of the ENIAC, what caused problems were literal bugs who crawled to the machine).
Sometimes bugs can be as disastrous as cracking your program the second you run it and ruin everything you´ve worked so hard for!!! and other times they´re not as bad, but either way the best thing to do is spray Raid over them and kill them(please don´t spread Raid ver your computer, that thing is really toxic).
Software testing is just what it sounds like, to run your own program and see how it works, so you can correct any mistakes you may have made. This is usually made in order to debug your program, or to give it maintenance(which a lot of times ´maintenance´ means a new bug was discovered). While it may seem easy, it often gives not-experienced programmers(like me) a really really hard time.
This is a huge topic and has a lot of coverage in it, so we´ll start from the beginning.
Why do we do it?
Well, first of all, a crash in your program carries a risk of damaging your hardware. Also the people funding or contracting you don´t want to pay for later debugging, because that is quite expensive. A study from the NIST in 2002 found that this is the cost of debugging at later phases of the development.
| Cost to fix a defect | Time detected | |||||
|---|---|---|---|---|---|---|
| Requirements | Architecture | Construction | System test | Post-release | ||
| Time introduced | Requirements | 1× | 3× | 5–10× | 10× | 10–100× |
| Architecture | – | 1× | 10× | 15× | 25–100× | |
| Construction | – | – | 1× | 10× | 10–25× | |
Table taken from NIST Study, 2002
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