If received and approved filenames are identical, tests spuriously pass

[claremacrae]

I was playing around with custom namers, and accidentally generated a namer that generated identical received and approved file names.

I then wrote a test that I expected to fail, as the approved content didn't match the source code.

However it passed!

And I eventually worked out that it was because it was effectively testing if received content matched received content, which always passes!

[claremacrae]

This will be fixed in the next release