Wal-Mart’s move last month to require its employees to adopt a new dress code at the workers’ expense is a test case for companies planning similar actions, according to Deborah Weinstein , a lecturer in Wharton’s legal studies and business ethics department. Under Wal-Mart’s new dress code, workers are required to wear collared shirts and khaki bottoms. The company will continue to supply for free the blue vests they currently wear. Wal-Mart’s action triggered outrage among worker unions, which are calling on the company to pick up the tab for the new attire. Weinstein, an employment law attorney, discussed the implications of Wal-Mart’s move — which she said could spur class-action lawsuits — on the Knowledge at Wharton show on Wharton Business Radio on SiriusXM channel 111 . (Listen to the podcast at the top of this page.) Legally, employers can require their workers to wear uniforms and also to pay for their cost and upkeep barring exceptions, noted Weinstein.…