tests: Add missing asserts

[kstrafe]

Some asserts were missing on is_ok and is_none statements. This patch adds those asserts.

[codecov]

Codecov Report

Merging #226 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #226   +/-   ##
=======================================
  Coverage   97.49%   97.49%           
=======================================
  Files          25       25           
  Lines        2357     2357           
=======================================
  Hits         2298     2298           
  Misses         59       59

Impacted Files	Coverage Δ
src/packet/header/fragment_header.rs	98.07% <100%> (ø)	⬆️
src/packet/header/standard_header.rs	98.59% <100%> (ø)	⬆️
src/packet/header/acked_packet_header.rs	98.07% <100%> (ø)	⬆️
src/infrastructure/arranging/ordering.rs	99.09% <100%> (ø)	⬆️
src/packet/header/arranging_header.rs	97.67% <100%> (ø)	⬆️

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[jstnlef]

Looks good 👍