I bring Peacock Productions, 364 NLRB No. 104 (Aug. 26, 2016), to your attention because the NLRB did a nice job of summarizing the applicable supervisory test. The Board held that the employer did not meet its burden of  establishing that certain NBC producers were exempt from the NLRA as supervisors, reasoning:

Section 2(11) defines a supervisor as any individual having the authority, in the interest of the employer, to (among other functions) hire, assign, or responsibly direct employees, so long as the individual exercises independent judgment in doing so. The burden of establishing supervisory status lies with the party asserting it. NLRB v. Kentucky River Community Care, 532 U.S. 706, 711–712 (2001). Conclusory evidence, in the absence of specific examples of the exercise of supervisory authority, does not satisfy that burden. See, e.g., Lynwood Manor, 350 NLRB 489, 490–491 (2007); Golden Crest Healthcare Center, 348 NLRB 727, 731 (2006). The party asserting supervisory status must show that the individuals in question have the authority to engage in at least one of the supervisory functions set forth in Section 2(11), that their exercise of that authority is not simply routine or clerical but requires the use of independent judgment, and that their authority is exercised in the interest of the employer. Oakwood Healthcare, Inc., 348 NLRB 686, 687 (2006).6 Supervisory status is not proven where the record evidence “is in conflict or otherwise inconclusive.” Republican Co., 361 NLRB No. 15, slip op. at 5 (2014) (citing Phelps Community Medical Center, 295 NLRB 486, 490 (1989)).

Mitchell H. Rubinstein