Tests are systematic procedures for measuring individual behavior and can be used by teachers to measure students' acquisition of knowledge, skills, and values. There are different ways to categorize tests, such as whether they are objective or subjective, standardized or unstandardized, and norm-referenced or criterion-referenced. Some common types of tests include personality tests, intelligence tests, aptitude tests, achievement tests, summative tests, diagnostic tests, formative tests, socio-metric tests, and trade tests.