This is extensively covered in many threads about taxes. There is a blue link below your post that will take you to those threads.
In general, reimbursements for required purchases is not taxable income. Keeping products provided free for testing, IMHO, probably also is not a taxable even as long as the items are of minor value. If they give you a Porsche to test and you get to keep it, that may be quite a different matter.
Based in MD, near DC
Shopping from the Carolinas to New York
Have video cam; will travel
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