A test is a way of checking something to see if it is true, or false, or if it is edible or not. If something can be tested, or finishes the tests correctly, it is testable. A test is different from an experiment: Before a test is done, there is an expected result. The test is performed, to show this result. In an experiment, the outcome is open. Very often, tests are performed as part of an experiment.
Products are usually tested for quality, and so that many customers will get the best products.
Rarely, people use "tests" to check people's hearts. For instance, in a famous rap song, in Korea, the lyrics were about a boyfriend, telling his girlfriend, "I'm sorry, but I must tell you we have to break up. I do not love you, I have to tell you. Forgive me, but I have to tell you. It's all a test." - Many people accuse this theory as an "excuse to be offensive" or an "excuse to break up with his girlfriend", so it does not count very logically in the "test" page.
In software engineering, a test is used to determine a characteristic of a software system. Software is tested before it is released. Alpha testing is where software developers check the software for bugs. Software can also be checked for quality and usability. Beta testing is done by groups of users.
Cars and other vehicles are tested using a crash test. The car is put under severe conditions to see what will make it fail. Other machines can also be crash tested. Crash test dummies stand in for humans. They 'sit' in the car seat to see if a human in the crash would have been injured or killed. Crash tests cost a lot of money.