S hares in telecoms testing firm Spirent Communications plunged by as much as 34.3% as it warned its clients are delaying their spending on infrastructure. The business expects a 20% fall in revenue this year as network providers which use Spirent to make sure their 5G services are not at risk of going down “continue to be very challenged”, and so are not spending on Spirent’s services. The business said that, after a weak start to the year, it had expected to see “a strong pick-up in orders from China”, which represents a large portion of its revenue. However, this…