What is the test for establishing a case of discrimination against a defendant in an employment action?

If a plaintiff successfully establishes a prima facie case of discrimination, "the defendant may rebut that showing by articulating a legitimate, non-discriminatory reason for the employment action." Weinstock v. Columbia Univ., 224 F.3d 33, 42 (2d Cir. 2000). "Upon the defendant's articulation of such a non-discriminatory reason, the presumption of discrimination arising with the establishment of the prima facie case drops from the picture." Id. (emphasis removed). The burden shifts back to plaintiff to "come forward with evidence that the defendant's proffered, non-discriminatory reason is a mere pretext for actual discrimination." Id.