TST: partial indexing with __getitem__ and integer labels

[toobaz]

• closes Wrong behaviour/error when indexing MultiIndex with list #12416
• tests added / passed
• passes git diff master --name-only -- '*.py' | flake8 --diff
• whatsnew entry

Just a test for the bug, which was fixed at some time in the past.

[codecov]

Codecov Report

Merging #16029 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #16029   +/-   ##
=======================================
  Coverage   90.99%   90.99%           
=======================================
  Files         153      153           
  Lines       50469    50469           
=======================================
  Hits        45924    45924           
  Misses       4545     4545

Flag	Coverage Δ
#multiple	88.76% <ø> (ø)	⬆️
#single	40.43% <ø> (ø)	⬆️

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[jreback]

still reviewing.

[jorisvandenbossche]

@toobaz Can you add the df[[1]] raising a KeyError case as well? (that also was incorrect at the time you opened the issue)

[toobaz]

@toobaz Can you add the df[[1]] raising a KeyError case as well? (that also was incorrect at the time you opened the issue)

yep, done

[jorisvandenbossche]

@toobaz Thanks!