Spark is confident it's streaming service for the Rugby World Cup will work, but has a contingency plan just in case.
The app will be available from 10 am to watch the opening of the Formula One in Melbourne and will be used as a way to iron out any problems.
Some Rugby World Cup games will be shown by TVNZ, but if the app doesn't work for other games it will show those too.
Spark's chief financial officer David Chalmers told Mike Hosking the company is confident the service will be able to cope with demand.
He says the company doesn't want New Zealanders to miss games, so in the unlikely event something goes wrong, there's a plan.
"You can do all of the testing you like behind the scenes, which we have been doing. Until it actually goes out live, that is when you get the true test of it but we have been adding features in the meantime which will improve over time."
Spark's head of Sport Jeff Latch says he expects - and welcomes - bug reports during Spark Sport's first 30 days, which are free.
He does hope that it's sufficiently up to scratch by the end of the month that the Bahrain Grand Prix (starting March 31) can be offered through Spark Sport only without any TVNZ safety net.
Spark Sport will also add support Google Chromecast, a $70 gadget for getting internet-delivered content to a regular telly and Apple Airplay (Apple's technology for wirelessly beaming content from an iPad, MacBook or iPhone to a TV, as long a that TV has an Apple TV unit attached).
Spark Sport can be accessed via Sparksport.co.nz or via iOS (iPhone, iPad) and Android apps.