Extract xref test code--customizable for odd duck, Troff

[idodeclare]

Hello,

Please consider for integration this maintenance patch for xref test classes to remove some redundancy.

Thank you.

[coveralls]

Pull Request Test Coverage Report for Build 4001

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 73.6%

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Totals
Change from base Build 4000:	0.03%
Covered Lines:	33560
Relevant Lines:	45598

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💛 - Coveralls

[tarzanek]

perfect, merging :-) thank you!