Some startups pick up a lot of traction without a whole lot of recognition for it. One such startup is Sauce Labs, which accumulated 3,500 customers for its cloud-based website and mobile app testing services. Today the startup is revealing a new $15 million funding round, which should help the growth continue.

In 2014, Sauce Labs’ revenue was up 145 percent over the prior year. Now the San Francisco-based startup can build out more of a European presence with data center infrastructure and some new salespeople, Sauce Labs chief executive Jim Cerna told VentureBeat in an interview.

The customer list features several big names, including Intuit, PayPal, Sony, Shutterfly, Staples, and Visa. And yet, Sauce Labs hasn’t picked up a buzz the way developer-friendly startups like GitHub and New Relic have. Perhaps as the customer list grows, that could change.

Sauce Labs’ testing services are based on the Selenium and Appium open-source tools.

Competitors include HP, with its application lifecycle management line of software, as well as startups like BrowserStack. And of course, Sauce Labs also knows engineers have home-brewed tools for testing apps and websites on multiple browsers and operating systems. But maintaining such systems can be “a difficult task,” Cerna said.

Sauce Labs started in 2008. More than 100 people should work for the startup by year’s end, Cerna said.

Existing investor Toba Capital led the new round. To date the startup has raised $36 million.