Tests and measurements are available as commercially standardized tests or unpublished.
Commercially standardized tests (Published tests) are available for purchase, you may pay for both use of the test and for the scoring key. These tests have been researched and established norms have been developed.
Unpublished tests are usually located in journal articles. Before use, permission for use should be requested from the author or publisher.
Information sources regarding tests:
A good place to start to learn about tests is the American Psychological Association's FAQ/Finding Information about Psychological Tests.
This resource was prepared by the Joint Committee on Standards for Educational and Psychological Testing of the American Educational Research Association, the American Psychological Association, and the National Council on Measurement in Education. It "reflects changes in federal law and measurement trends affecting validity; testing individuals with disabilities or different linguistic backgrounds; and new types of tests as well as new uses of existing tests.