Update: Consumer Reports has given the new MacBook Pros a "Recommended" rating after re-testing them. The publication does note that the 13-inch MacBook Pro without a Touch Bar does significantly outperform the Touch Bar model despite Apple's claims that the two have the same battery life, which is in line with the findings in our reviews.

Original story: In late December, review publication Consumer Reports made headlines by failing to provide a "Recommended" rating to Apple's latest MacBook Pros. It was the first time any of Apple's MacBooks had failed to earn the rating. In the publication's testing, the laptops' battery life varied wildly, sometimes lasting as long as 19.5 hours and sometimes as little as 3.75 hours. The publication didn't have these problems with older MacBook Pros or with any of the 140 other laptops it has rated.

After working with Apple over the holidays, Consumer Reports now says that the problem was caused by an "obscure" Safari bug specific to page caching, which the publication disables when it runs its battery tests. To test battery life, Consumer Reports sets laptop screens to a specific brightness level and then loads a series of webpages in the laptop's default browser (Safari in this case) in a loop until the battery dies. Apple suggests that disabling browser caching for a test like this doesn't reflect real-world use, but it does make sense for a synthetic test—users will continually read new pages rather than visiting the same static pages over and over again, so Consumer Reports wants to make sure that its test is actually downloading data over the network rather than simply reading cached data from the disk.

Apple says it has fixed the bug in the latest macOS Sierra beta that it released to testers yesterday, the third beta of version 10.12.3. The 10.12.2 update "fixed" inaccurate battery life estimates in the new Pros by disabling the battery life estimate entirely across all Mac laptops that run Sierra.

Browser bug or no, Consumer Reports hasn't been the only publication to report disappointing battery life from the new MacBook Pros. We covered some of the reasons why the new laptops' battery life is more usage-dependent than in the previous model and how the GPU and the new Touch Bar could be affecting battery life. It was also reported that Apple originally planned to use a different kind of battery in the MacBook Pros, one that was contoured to the case to maximize its size a la the 12-inch MacBook. Problems reportedly found during the development process forced Apple to use a more conventional battery with less capacity.

Consumer Reports says it will re-test the laptops' batteries and revisit its rating depending on what it finds.