Many tests are commercial products. They are created for professional use and are usually available for use only by professional psychologists.
Mental Measurements Yearbook with Tests in Print contains reviews of commercially available tests and measures. Although you will find reviews of tests in this database, you may not be able to acquire the test you find described in the review.
Psychological tests and measures are not collected by the library. Some libraries do collect these tests, but their use is restricted to local users and they do not circulate. It is a good idea to confirm with your instructor whether or not you need the actual test instrument for your assignment before trying to obtain it.
PsycTESTS provides information on non-commercial tests and measures. Most of these tests (in whole or in part) can be found in this database (look for records with the full text PDF attached). They can also be found appended to articles in the PsycINFO database. Many of these are freely available to use for research and education, but you may have to contact the author/publisher for access to the complete test instruments.
See APA's "Statement on the Use of Secure Psychological Tests in the Education of Graduate and Undergraduate Psychology Students" for more information on the educational use of psychological tests.
Many research articles provide information about the instruments used in the study, and some include partial or complete test instruments.
Use Advanced Search in all databases.