Testing can show the presence of lots of defects but not prove that there are not any more defects

What other than Software can be tested?

All stuffs need to be tested to understand the cost risk of failures.
i.e: http://www.internetautoguide.com/10-8-79/toyota-recalls.html
http://www.foxbusiness.com/personal-finance/2011/05/18/toyota-consumer-lawsuit/

Why not?

What is test objective?

There can be different test objective:
1. Finding defects?
2. Gaining confidence about the level of quality and providing information.
3. Prevent defects?
Test Objective may vary depend on test type/test phase. It also defines for the name of test type.
1. Introduction testing early in SDLC prevent defects.
2. Requirement analysis (Static testing) also prevent defects appearing in the code.
3. Development testing: to cause as many failures as possible so that defects in sw can be identified and fixed.
4. Acceptance testing: to confirm that the system works as expected, to gain confidence that it has met requirements.
5. Maintenance testing: to ensure no new defects have been introduced during development changes.
6. Operational testing: to assess system characteristics such as reliability or availability.