Some authors will include copies (or abridged copies) of the tests they used in the journal articles they publish. They will also often discuss the test itself and any limitations, or changes they made.
It's not always possible to find the full text of an instrument. Try these tips:
• Google the test to see if it's commercially available or if the author has given permission to use it
• Search databases for an appended copy of the test (see Find tests in journal articles above)