Product testing and quality certification group Intertek said it traded in line with expectations in the first four months of 2015 amid continued weakness in oil, gas and minerals spending but good growth elsewhere.The company, whose chief executive officer Wolfhart Hauser will step down from the board on Friday after 10 years, reported revenue growth of 3.3% for the period.Foreign exchange movements also had a 2.4% positive impact on the top line due to a stronger pound.Constant-currency organic growth came in at just 0.3%, though when excluding the effect of Intertek's decision to exit certain low-value industry contracts, underlying growth would have been 1.9%.The product divisions of consumer goods and commercial & electrical both saw good growth, with strong demand for textiles testing in particular. The chemicals & pharma division also grew modestly.However, lower demand for services for oil and gas capital projects continued to affect in the industry & assurance division, along with its exit from certain contracts.In the commodities uni, revenues from the minerals markets declined after the ore export ban in Indonesia and weak minerals market conditions overall.Intertek said its organic revenue growth expectations remain unchanged for the full year. Looking to the medium term, its expected "mid single-digit organic revenue growth" as oil and gas capex headwinds ease.As previously announced, André Lacroix will join the company as CEO from 16 May.Hauser said: "After 10 years as CEO, and more than 30 years in the industry, I would like to thank the employees and shareholders of Intertek for their support. I am confident in the positive long term growth opportunities for Intertek and the 'TIC' industry."The stock was up 0.4% at 2,717p in early deals on Friday ahead of Intertek's annual general meeting.