See image. If I copy the text to an editor, the text is (two underscores):
"Expected: File 'result1_2.xml' should_exist"
This often causes us confusion, for instance with typenames that end up in the log and have underscores, but more importantly, path names or strings that are compared and suddenly have spaces. In the screenshot, the text " HG-ALL " is in fact "__HG-ALL__". Also, when I select the text, the redrawing or coloring does not reveal that there are actual underscores.