Finding tests in ERIC varies a little, depending on which version you are using:

• Dept. of Education's version-- put in terms (such as student motivation) and then choose Tests/questionnaires from the Publication type menu.
• Ebscohost/Ebsco--type tests/questionnaires in one of the search boxes.
• ProQuest version--choose tests/questionnaires in the Document Type menu.

Included tests will usually appear in the appendices of the article or dissertation.

If you don't have a specific test in mind, put in words that describe what you are interested in, combined with the tests/questionnaires phrase or (survey* or instrument* or assessment* or evaluation* or measure* or questionnaire* or scale*). If you aren't finding what you need, use alternative terms to describe what you are looking for--the thesaurus lists the indexing terms, also called descriptors.