What is the test for dismissing a motion for failure to prosecute diligently?

thereby forcing the defendant to incur additional time and expense. See In re Eisen, 31 F.3d 1447, 1452-53 (9th Cir. 1994) ("When considering prejudice to the defendant, 'the failure to prosecute diligently is sufficient by itself to justify dismissal, even in the absence of a showing of actual prejudice to the defendant from the failure.... The law presumes injury from unreasonable delay.'") (quoting Anderson v. Air West, 542 F.2d 522, 524 (9th Cir. 1976)).