NASA is not developing a warp drive.

A researcher at a NASA facility published a theoretical paper about warp drive and mentioned that NASA's Advanced Propulsion Physics Laboratory was working on a warp field interferometer that can measure spacetime disturbances. That story got blown out of proportion in the media. There is a big difference between an interferometer and an engine.

APPL is tasked with examining theoretical propulsion technologies to see which ones could be brought to practical use in the near future, as NASA examines its options for outer solar system exploration. They are looking at the physics behind a lot of ideas - that doesn't mean they are building engines.