A split test (or an A/B test) is just a comparison between two different variants of a website, advertisement, email, or online form. To this end, an original version (Split A) is compared against a modified version (Split B). Here’s a basic example: You want to optimize an ad’s performance, but you aren’t sure which changes will deliver results. So you create a version of the original ad (B) and display it to a predefined target group. Next, you split the traffic into two equal halves and assign an ad variant to each. Now you are in a position to compare the results of each variant and use the insights to optimize your ad.
Google itself offers the possibility of split testing for AdWords Search network campaigns, naming this feature “Campaign Drafts and Experiments”. There you can test various changes within your campaign, for example ad variants to be tested against the current settings. That said, this option is only available for text ads and for the Display network. Unfortunately, the feature is not available for Google Shopping.