The robotic Roomba vacuum cleaner has a new partner. iRobot’s Scooba is an automatic mop that is slightly larger and heavier than Roomba and costs $399. It comes with a battery charger, a battery pack, cleaning solution, a spare front-wheel assembly, and a battery-powered “virtual wall,” which sends out an infrared beam that Scooba won’t cross. You’re supposed to remove rugs or furniture, as you would during mopping. Scooba isn’t for unsealed or laminated wood floors.

Scooba spirals around the room until it bumps into an obstacle, then follows its edge or sets off in another direction. It sweeps up debris, squirts in the cleaning solution, then slurps up the dirty solution into a holding tank. When finished, it dries itself so that it won’t drip when you pick it up. Then it beeps when it’s done.

How we tested. In a tiled lab room, we placed a chair, a stool, and a table, and a drop of mustard for every foot of tile. Then we let Scooba loose and kept track of how many of our 236 mustard spots it disturbed. We also measured how much cleaning solution Scooba left on the floor, and compared how many scrubs it took Scooba to remove a dried-in stain vs. how many strokes it took a mop. Finally, we sent Scooba home with nine staff members for real-world cleaning.

What we found. Scooba covered most of the floor, 83 percent, but had trouble with corners and edges. It didn’t leave the floor slippery. Scooba and the mop easily wiped up coffee, grape juice, and tea stains, but the mop was better with stubborn stains (crayon, shoe polish). Scooba’s tank of solution lasted 50 minutes, and it was less noisy than an upright vacuum. At-home testers found it fine with most light dirt, but said it didn’t remove heavier accumulations and wouldn’t fit around the toilet, leaving them to mop the bathrooms.

The bottom line. Don’t toss your mop. It cleans faster and more thoroughly than Scooba, and costs far less.