Google CEO Larry Page AP Google wants the stores that buy its search ads to have every confidence their advertising investments are paying off.

According to the Wall Street Journal, the tech giant is rolling out a test campaign to track the purchases people make at brick-and-mortar stores after clicking on a Google search ad for a given store or product.

In order to make these determinations, WSJ says Google is partnering with data collection companies like Acxiom and DataLogix, which track what customers buy when they use their loyalty rewards cards or redeem other marketing offers.

By matching this anonymous consumer information from the data providers to web-based tracking cookies, Google can determine how many products were purchased by people who clicked on a given ad and how much more money those people spent than consumers who didn't.

WSJ reports the test run will include about six advertisers, including Michaels craft stores.

While Google has long since convinced online retailers like Zappos they need to be buying its search ads, the new test campaign is part of a larger push to show brands its ads persuade people to make in-store purchases, sometimes days and weeks after seeing an ad online.

This past fall, it announced it would offer store advertisers the ability to measure how many people saw their ads and then visited a brick-and-mortar location while logged into Google on their smartphones, provided the people in question have consented to sharing their location data.

Rival online ad giant Facebook has offered customers similar in-store purchase data since 2012 through its own partnership with DataLogix, but Google's partnership could potentially be more potent because of its scale.

Google's AdWords search business is the most effective ad product in the history of the internet, helping Google grab more than 40% of the entire U.S. digital advertising market.

By proving its search ads work for as well for offline stores as they do for e-commerce, Google could start luring money from the grocery and supplies stores that have previously stuck to advertising in print and on television.