UK-listed Intertek is one of the world's three largest testing companies alongside SGS and Bureau Veritas. Intertek is one of the FTSE 100 companies that many investors haven't heard of but whose performance has been strong. Its business is to ensure the quality and safety of its customers' products, processes and systems.

Intertek listed in 2002 and has performed well for shareholders since then. In 2002 earnings per share were just 27.1p. Fast-forward to 2016 and earnings per share came in at 167.7p.

The testing sector has a number of growth drivers and Intertek has undertaken a number of acquisitions since listing. Recent trading at Intertek, though, has been hit by weakness in its resources division. However, the other two divisions – products and trade – have continued to generate revenue growth.

Product testing is the main driver of the business, generating 58 per cent of first-half revenue and 73 per cent of profit.

The top line result for Intertek in H1 2017 was modest with organic revenue growth up 1.7 per cent to £1.355 billion at constant currency exchange rates. Total revenue at reported rates, though, rose 13.9 per cent.

The shift towards the products serves to improve Intertek's growth rate and profitability. The products division delivered a first-half margin of 20.5 per cent and is forecast to grow at rate faster than GDP. The trade division, which accounted for a quarter of first-half revenues and one-fifth of earnings, is expected to grow at the rate of GDP. It generated a 14.1 per cent profit margin in the first half.

The product division recorded 5.8 per cent organic revenue growth, against 4.6 per cent organic growth in the trade division.

Overall, the operating profit margin improved by 1.1 percentage points at constant exchange rates and by 0.9 percentage points at reported exchange rates. The margin improvement meant that constant currency earnings per share improved 11.4 per cent, despite only 2.7 per cent revenue growth. Reported earnings rose 21.3 per cent to 90.4p on the back of the 13.9 per cent increase in reported revenue.

Intertek's balance sheet also improved on a year ago, with net debt falling to £696m from £887m at June 2016. This was partly due to a £75m increase in free cash flow in the first half of 2017 on a year ago to £124m. The June 2017 net debt to EBITDA ratio of 1.3 times leaves plenty of scope for further acquisitions. Intertek states that this remains a fragmented market and as such further deals are unlikely to raise competition issues.

Intertek has an outstanding track record over the last 10 years, with earnings per share growing in every year from 2007 to 2013. This highlights the defensive nature of the business and the company's long-term customer relationships. The valuation for Intertek is on the face of it demanding, but this must be set against a robust track record and a strong long-term outlook. The forecast earnings multiple for 2018 is 23 times and the yield 1.6 per cent.

Greg Smith is the head of research at investment research and funds management house Fat Prophets.