test: Support asserting on doc index in test results

[AndrewSisley]

Relevant issue(s)

Resolves #2785

Description

Support asserting on doc index in test results.

PR does not seek to propagate it's usage, only to permit it's usage.

How has this been tested?

I also checked that it fails correctly if the results do not pair up.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.90%. Comparing base (2efd29a) to head (f29dc92).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2786      +/-   ##
===========================================
+ Coverage    78.77%   78.90%   +0.13%     
===========================================
  Files          315      315              
  Lines        23835    23835              
===========================================
+ Hits         18775    18807      +32     
+ Misses        3680     3659      -21     
+ Partials      1380     1369      -11     

Flag	Coverage Δ
all-tests	78.90% <ø> (+0.13%)	⬆️

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see 16 files with indirect coverage changes

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[fredcarle]

LGTM