I ran your test and avast acted just as it should.
The file is malicious, extension not withstanding.
It’s the file avast is detecting not just the extension.
You may, if you so desire (why I do not know) add the file
to your exclusions list. GUI>Settings>Antivirus>scroll down to “exclusions”.
This might help you http://www.eicar.org/86-0-Intended-use.html