There's a range of tests that helps the employer choosing the right candidate for the job - some work great, some less so. The tests measure different aspects of the candidates, with the intention to identify whoch candidates have the characteristics that makes them the most suitable to perform the tasks of the job, and to function in an optimal way during the conditions offered at the specific work.
Tasks and workplaces obviously differ a lot. At some workplaces, stress resistance is a very valuable characteristic, at others stamina is just as important, and at others the demand for social competence can be the dominating factor.
Roughly, one can divide these kind of tests in three different categories: personality tests, competence tests and aptitude tests.
Personality tests are made to describe the test subject's personality, meaning the inclination to act in a certain way. There is no standardized definition of personality, so the tests can differ quite a lot. Generally, they're built on self-assessment (meaning that the subjects get to answer questions on how they perceive themselves or how they would act in certain situations). The number of test types is large. Among the more well known are the Big Five personality test, DISC and Myers-Briggs.
Aptitude tests are measuring the test subject's ability to reason logically. They evaluate different aspects of the subject's logical thinking, by measuring the ability to think abstract, absorb complex information and uncover and use rules. As with personality tests, there are many types of aptitude tests. Some are supposed to be independent of the test subject's cultural background. SquidFactor prepares you for a wide array of different types of aptitude tests.
When the employer is looking for specific abilities, one is talking about competence tests. The tests are designed to simulate situations that the subject regularly encounters in the job, such as sorting assignments, mechanical reasoning or programming exercises. Often, the tests are tailormade to the employer's need.
Tests of different kinds are often used together to give the employer a coherent image of the candidate. Sometimes the tests are woven together, so the candidate performs several type of tests in the same session.
The selection process is different in different organisations, and can be run by different princples. Some tests candidates in an early stage to filter out the least appropriate candidates, whilst others test the final group to use the result as a basis for discussions with the candidate - and every thinkable combination in between.