Issue #4051: Added test for assertFileNotEqualsCanonicalizing

[alecsmrekar]

Linked to issue: #4051

I first test if the method checks the existence of both the expected and actual files. I then test if the method correctly asserts that the files have different contents.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (67cfab0) 89.34% compared to head (c216f7e) 89.37%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4647      +/-   ##
============================================
+ Coverage     89.34%   89.37%   +0.03%     
  Complexity     6425     6425              
============================================
  Files           683      683              
  Lines         20405    20405              
============================================
+ Hits          18230    18237       +7     
+ Misses         2175     2168       -7     

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[sebastianbergmann]

Thank you for your contribution. I appreciate the time you invested in preparing this pull request. However, I have decided not to merge it: the test method you propose does too much.