Enable running of tests in tests/db_engine_specs

[robdiciuccio]

CATEGORY

Choose one

• Bug Fix
• Enhancement (new features, refinement)
• Refactor
• Add tests
• Build / Development Environment
• Documentation

SUMMARY

Tests in tests/db_engine_specs are not currently running, due to nosetests requiring an __init__.py to recognize the folder as a module.

Before: Ran 504 tests in 124.049s (py36-sqlite)
After: Ran 619 tests in 121.567s (py36-sqlite)

Also includes a refactor and tests from #8733 in order to preserve cherry-picking.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

Ensure db_engine_specs tests are running locally and in CI.

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

REVIEWERS

@willbarrett @craig-rueda @dpgaspar @villebro

[codecov-io]

Codecov Report

Merging #8902 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #8902   +/-   ##
=======================================
  Coverage   58.97%   58.97%           
=======================================
  Files         359      359           
  Lines       11333    11333           
  Branches     2787     2787           
=======================================
  Hits         6684     6684           
  Misses       4471     4471           
  Partials      178      178

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[villebro]

Nice catch! LGTM

[willbarrett]

Ouch. That's no good! Good find, and thank you!