U.S. Army soldiers have completed intensive testing of Microsoft’s new multifunction goggle — and the results may determine whether Congress rejects most of the $424.2 million proposed in next year’s defense budget to keep buying them.

Over three weeks ending June 18, 70 Army infantry wore the devices during three 72-hour scenarios involving movement toward an enemy, an attack and a defensive mission, according to Jessica Maxwell, a spokeswoman for the Defense Department’s testing office. The results are projected to be released in September.

Microsoft aims to develop a “heads-up display” for U.S. ground forces similar to those for fighter pilots. The Integrated Visual Augmentation System, or IVAS, would let commanders project information onto a visor in front of a soldier’s face and would include features like night vision. It’s a customized version of the company’s HoloLens goggles. The Army has projected spending as much as $21.9 billion on the devices, spares and support services over a decade if all options are exercised.

Although the results of this month’s testing won’t come until late in the annual congressional budget process, they are likely to shape final negotiations among lawmakers, some of whom have signaled they aren’t ready to commit to buying the goggles.

This month, the House Defense Appropriations subcommittee adopted a draft budget that would cut all but $24.2 million of the Pentagon’s $424.2 million procurement request for the fiscal year that begins Oct. 1. The panel’s report cited “questions still outstanding regarding the production viability” of the goggles. Its Senate counterpart expressed similar skepticism in the current year’s defense legislation.

Army Secretary Christine Wormuth last month expressed confidence that the combat testing this month wouldn’t disclose any major issues.