What is the test for fair use in the context of copyright law?

^3. As we have explained, "[f]air use is a judicially created doctrine dating back nearly to the birth of copyright in the eighteenth century, but first explicitly recognized in statute in the Copyright Act of 1976." On Davis v. The Gap, Inc., 246 F.3d 152, 173 (2d Cir. 2001) (internal citations omitted). Under that statute, to determine whether the use of a work is a fair use, courts consider four factors, including: