Read content file outside of eval block

[atoomic]

spec_helper is sneaking in some content from a file to a namespace.

But it's not required to read the file inside the quoted eval.

Reading it earlier provides the advantage of building the OP tree for it, so we can use Test::Mockfile without impacting this test module.

It also reduces the length of the string eval and optimize it and make it easier to maintain at the same time.