Well, avast (as well as all other av’s that I’ve tested with) doesn’t know.
I have attached two files to this post.
Both have the eicar test string in them.

Since this webboard doesn’t allow .com files, I’ve named it .png
Download it and rename it to Noname1.com.
That is the original file name.

Noname1.txt is only has the eicar test string in it.
Noname1.com has the exact same string in it, but I’ve added 7 characters in front of it making it look like a real .com file.

If you try to “run” the .com file it will just “run” and no alert is given by any of the av’s I’ve tested it with.
If you open the .txt file no av I’ve tested it with wil give a alert.

If you right click the .com file and choose scan, no av will give a alert.
You can even double click the .com file and it will “run” without a alert.

If you right click the .txt file and choose scan, all will detect the eicar string and give a alert.