[tahoe-lafs-trac-stream] [Tahoe-LAFS] #3519: Stop using the mock library for testing

[Tahoe-LAFS]

#3519: Stop using the mock library for testing
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 Reporter:  exarkun  |          Owner:  exarkun
     Type:  defect   |         Status:  new
 Priority:  normal   |      Milestone:  undecided
Component:  unknown  |        Version:  n/a
 Keywords:           |  Launchpad Bug:
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 Some discussion about motivations for this

 *
 https://nedbatchelder.com/blog/201206/tldw_stop_mocking_start_testing.html
 to start
 * ​https://pythonspeed.com/articles/verified-fakes/
 * ​https://martinfowler.com/articles/mocksArentStubs.html

 Instead:

 * Where possible, we will completely remove whatever role the mock is
 serving from the test and focus on more well-defined, isolated units of
 functionality.
 * Failing that, where possible, we will use the implementation that is
 used under real usage of whatever the relevant interface is.
 * Failing that, we will use verified fakes of whatever the relevant
 interface is.

 This is a tracking ticket for various other tickets which make progress
 towards this goal.  There are too many uses of mock to address this all at
 once.  Fortunately each use should be essentially independent from the
 rest so the task is easily broken up.

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Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/3519>
Tahoe-LAFS <https://Tahoe-LAFS.org>
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