Facebook is quietly making its “Credits” virtual currency a more integral part of the site, and on Friday the most recent Credits test went live. In this test, a new portion of the application directory features apps that integrate Credits as a method of payment, and users will be encouraged to install those applications and buy more credits, according to screenshots taken by software developer Jesse Stay.

Facebook says it’s testing the feature with a very small percentage of users.

Here’s how the new interface looks. Credits are featured in a new drop-down menu on the top navigation bar, which appears on every page of the site. The button lists the number of Credits you currently have deposited in your account, and if you click on it, you can see a menu with a list of options for spending Credits, buying more Credits, or learning more about how the virtual currency works.

If you click on “Spend Credits,” you’ll be taken to the “Credits Enabled” portion of the app directory. You’ll then have the option to install these applications, spend Credits in them, or buy more Credits to use.

Facebook is still only testing credits with a few third-party applications, so there aren’t many apps to choose from yet.

However, the fact that Facebook is linking to apps that use credits from the navigation bar could mean Facebook will be driving a lot more users to look for apps with Credits. Assuming Facebook eventually rolls out this feature to all of its users, developers will have a big new incentive to add Facebook Credits to their payment system.

Facebook has also been busy testing out other virtual currency features. Last week, it also introduced a way for people to buy Credits through their phones, in partnership with mobile startup Zong.