Ping-Pong Programming (aka. Ping-Pong Pair Programming) is a kind of Pair Programming that TDD (Test Driven Development) is included while in practice. In other words, it is a combination of Pair Programming and TDD.
In addition to the Pair Programming's own benefits, Ping-Pong Pair Programming has the following advantages:
Easier to find the rhythm of the development flow which can be a problem when it comes to switching pairs.
A much smaller problem space needs to be managed, so this enables developers to sync with the flow quicker than other styles.
Avoids mismatched pair issues -like one developer knows more than the other- as each developer takes turns writing tests and making them pass.
The work is gamified, so it puts another kind of motivation for developers.
Let's say there are two developers, developer A and developer B. The development flow goes like the following:
A writes a failing test.
B makes the test pass writing only enough code to make the test pass.
B writes the next test.
A writes only enough code to make that test pass.
Continue until A and B both agree that there are no more tests for the unit they are currently working on.
Either developer can refactor the code only all tests stays "passing".
The optimal setup to work in this rhythm is two developers sitting side by side, a single computer with two input devices: That’s two monitors, two keyboards, and two mice. However, developers may do pairs remotely if they work in a remote environment via tools like Live Share etc.
Ping-Pong programming can also be done in a group which is a form of Mob Programming. So it can be called Ping-Pong Mob Programming:
A developer writes a failing unit test.
Another developer -maybe the one next to her/him- writes as little code as possible to make the test pass.
Another developer -maybe the one next to her/him- writes a failing unit test. And it continues like this...
Any developer can refactor any code when needed but only when the tests pass.
When the driver asks for help, the rest of the group politely helps out without any other interruption.
Check out these great links which can help you dive a little deeper into running the Ping-Pong Programming practice with your team, customers or stakeholders.