According with our documentation:

• JUnit Report Macro

We should see a screen like this:

However in Confluence 5.1.2, we see a screen like this:

How to replicate:

1. Running Confluence 5.1.2, create a page, and try to insert a JUnit macro.
2. Place the file in your filesystem, and put the full URL there: file:///C:/TEMP/
3. You'll see a screen like this.