Feature: Archive header
The header consists of the following elements:
* Four (4) LE bytes, which in ASCII represent `\xffBOX` named `magic_bytes`
* a 32-bit unsigned LE integer field named `version`
* a 64-bit unsigned LE integer field named `alignment`
* a 64-bit unsigned LE non-zero integer field named `trailer`
Scenario: A valid .box header
Given a valid .box header
When the header is parsed
Then a valid header is returned
Scenario: An invalid header
Given an invalid header
When the header is parsed
Then an error is returned