This LibGuide has an extensive explanation of several different ways of searching for published assessment instruments (tests): GSE 80300
Reviews and purchasing information are available for many tests in the Mental Measurements/Tests in Print database. No full-text access to tests is available in this database.
APA PsycNet -- PsycTESTS contains just over 2,000 test names and 1,528 actual unpublished tests. The main focus of the database is unpublished tests. Some full-text tests are available. Basically, these are tests that were developed as part of a journal article, in order to gather data for the authors' study.