Add ECS script to composer.json and update testing.md.

[terabytesoftw]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 17.16%. Comparing base (b61fa20) to head (2a1e524).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main      #11   +/-   ##
=========================================
  Coverage     17.16%   17.16%           
  Complexity      125      125           
=========================================
  Files            14       14           
  Lines           268      268           
=========================================
  Hits             46       46           
  Misses          222      222           

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