Investing.com - Even the best get put to the test.And that seems to be the case with Apple.Suddenly, Wall Street analysts are lining up to warn about the tech giant's iPhone business, triggering a slump in its share price.Nomura Instinet started the negative cycle, calling Apple an "uninspired investment," warning investors to brace for disappointing iPhone sales and earnings. Morgan Stanley (NYSE:MS) slashed its estimate for handset sales in the previous quarter as well as the current one. Another firm, Mirabaud, suggested Apple will discontinue its iPhone X because it's too expensive.But iPhone sales worries have turned out to be over-done or even unmerited in the past. Amid the gloom, one firm, BTIG Research. counters that it is very early in the current quarter, and even though "headwinds" to sales are apparent, it is unclear if the slowdown will be as "dramatic as forecast."Apple also has a growing services business, which is sometimes underappreciated as a profit driver. On top of that, the company is also expected to return billions of dollars in cash to shareholders in the form of stock buybacks and dividends. Apple shares (NASDAQ:AAPL) are flat on the year but up 22% in the past 12 months. The company is expected to report earnings on May 1.