FiledownloadTest.TestDownload_WithExpectedFileName_DeleteFilesRemovesDownloadedFiles fails every 2 Weeks or so on TC. Locally, this can be reproduced by repeating the test around 500 times.
The reason the the test fails is that the downloaded "SampleFile.txt" is sometimes downloaded as an empty file with 0KB size, even though the file is not empty on the "server" aka the test site and broke support for downloading empty files.
This bug was until now only observed in Firefox, and we cannot say if this is a new Firefox issue or an old one that became apparent ever since we adapted our download infrastructure.
This bug may even be tied to the way we are hosting our testing site (perhaps the test site's download button is not setup correctly).
Also Note: this does not appear to be a timing issue. Upon hitting a break point and inspecting the file manually, it is indeed empty and does not stop being empty even after a prolonged amount of time.