Fix WhereAreMyBooksScript test that was marked as skipped

[jonathangreen]

Description

Update the test_overall_structure test, and remove the skip mark on it. The main thing that was causing issues in the test was that the test DB wasn't being passed into the script initialization.

Took the time while I was looking at the test to replace the custom mock with a couple magic mock functions as well.

Motivation and Context

Nice to not have any tests marked as skipped.

How Has This Been Tested?

Running tests.

Checklist

• I have updated the documentation accordingly.
• All new and existing tests passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.06%. Comparing base (81c439c) to head (5ade6fb).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1825      +/-   ##
==========================================
+ Coverage   90.03%   90.06%   +0.03%     
==========================================
  Files         299      299              
  Lines       39543    39543              
  Branches     8588     8588              
==========================================
+ Hits        35603    35615      +12     
+ Misses       2613     2601      -12     
  Partials     1327     1327              

Flag	Coverage Δ
manager	89.86% <ø> (+0.03%)	⬆️
migration	24.53% <ø> (ø)

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