This won't just be any test run, though. The Electron rocket will have a payload; Rocket Lab tweeted both Planet and Spire will have small satellites aboard the launch vehicle. Planet is has a huge network of small satellites which continually scan and image the Earth; it will send two of its Dove nanosats to orbit. Spire will send its weather-mapping and ship-tracking Lemur-2 satellites up as well.
The first Rocket Lab launch was considered a success, but the rocket didn't reach orbit. An in-depth post-flight analysis determined that it was caused by misconfigured telemetry equipment, which caused the launch center to lose communication with the rocket temporarily. When that happened, the flight was terminated, as per standard procedure. But the problem has been fixed, and Rocket Lab is confident that this second test will go more smoothly.
Competitor Vector launched a prototype of its rocket, the Vector-R, last month in a suborbital flight, and it was also carrying a customer payload. It's clear the small satellite space race is on; we'll see if Rocket Lab's will be the first of the two to make it to orbit.