Thanks for providing a copy of your project. A number of your tests do indeed contain corruption. Please see the attached screen shot for an example. I saw this by right clicking the test in the Solution Explorer, choosing "Open With," and then "XML (Text) Editor with Encoding."
Simply removing the corruption or commenting it out will not likely return the affected tests to a workable state. It is impossible to know if more critical lines were lost or replaced by the corrupted lines.
The good news is that the bulk of the XML data is retained in your corrupted tests. You may be able to edit a corrupted test and a working test side by side, deduce what information was lost, and reinsert it.
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