Use autospec in patches, also remove useless test

[DominicOram]

Fixes #812

To test:

1. Confirm tests all still pass and removed test is out of date

[codecov]

Codecov Report

Merging #813 (6cd2c89) into main (cf1e9fc) will increase coverage by 1.12%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #813      +/-   ##
==========================================
+ Coverage   93.33%   94.46%   +1.12%     
==========================================
  Files          37       37              
  Lines        1875     1878       +3     
==========================================
+ Hits         1750     1774      +24     
+ Misses        125      104      -21     

Impacted Files	Coverage Δ
...emis/experiment_plans/optimise_attenuation_plan.py	94.35% <100.00%> (+17.49%)	⬆️

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