See flat files made by the TFS build process.

On the main landing "page" of the Team Explorer tab in Visual Studio 2017, the one you can always return to by clicking on the "Home" icon that looks like a little house at the top of the pane, there will be a "Builds" button in a set that is My Work, Pending Changes, Source Control Explorer, Work Items, Builds, Reports, Documents, and Settings. Click here. Then click "Actions" and after that "View Controller Queue" from the little menu which appears. The "Build Explorer" tab appears and from here one may right-click on the items listed and pick "Open Drop Folder" to see flat files made by the build process. In the "TestReports" folder in the "Logs" folder in the particular setup I am looking at now there is a single .xml file. Search for "failures" in there. Also double-clicking on any one item in the "Build Explorer" folder opens up a little splash page on that item. Errors will be listed there as well.