Add regression tests

[phofl]

Search for a minimal example and the confirmation that it's fixed. Add the test then

• pd.core.groupby.groupby.DataFrameGroupBy.nth yielding false values with Interval MultiIndex Interval pandas-dev/pandas#24205
• Inconsistent behavior when DataFrame with strings and None is created from lists or dictionary.  pandas-dev/pandas#32218
• BUG: concat_{categorical, compat} leads to erroneous result on non-ns datetime-EA  pandas-dev/pandas#33331
• BUG: grouping with categorical interval columns pandas-dev/pandas#34164
• BUG: category index levels casted to non-category dtype in merge pandas-dev/pandas#37480
• BUG: iterrows encounters OverflowError with str and datetime64[ns] columns pandas-dev/pandas#35665
• BUG: series created from pyarrow array with date32 type in 1.5rc0 can be created but not displayed pandas-dev/pandas#48238
• BUG: dt.total_seconds() gives the wrong number of seconds pandas-dev/pandas#48521
• BUG: groupby.rolling.corr incorrect/fails when grouping columns contain tuples pandas-dev/pandas#44078
• BUG: v1.3.0 Introduces Unexpected Retyping of Categorical Column with NaN inside pandas-dev/pandas#43996
• "TypeError: unorderable types" in Python3 when index values are dict keys of tuples or tuples with non-homogeneous dtypes pandas-dev/pandas#22077
• pivot_table produces inconsistent columns if applied to empty table pandas-dev/pandas#21932
• DataFrame.from_dict multilevel dicts with datetime.date objects as keys sets the values as NaN in the DataFrame pandas-dev/pandas#19993
• BUG: .drop() doesn't parse strings for DatetimeIndex. pandas-dev/pandas#5355
• Pandas groupby sum misbehaves when one of the columns has string objects. pandas-dev/pandas#24196
• BUG: reset_index() Fails on a Series/DataFrame Object that has "False" (bool type) as the Index Name pandas-dev/pandas#38147
• BUG: Unexpected behavior math operations using multiindexes pandas-dev/pandas#51500
• ENH: allow complex type inference in astype/convert_objects pandas-dev/pandas#4895
• COMPAT: Floating point fractional hours for timedeltas gives unexpected precision issue pandas-dev/pandas#9048
• Inconsistent behaviour when assigning to series? pandas-dev/pandas#25548
• IntervalIndex level in MultiIndex does not work as expected pandas-dev/pandas#25298
• REGR: setting column with setitem should not modify existing array inplace pandas-dev/pandas#33457
• BUG: iloc.__setitem__ with a numpy array throws a TypeError expecting 1-D list pandas-dev/pandas#33828
• Assigning column with DataFrame(dtype='category') doesn't preserve categorical dtype, but Series does pandas-dev/pandas#31581
• .loc assignment with empty label list should not convert dtypes pandas-dev/pandas#29707
• columns sometimes not added to empty dataframe pandas-dev/pandas#28871

[vagechirkov]

Hey, I would like to work on this issue: pandas-dev/pandas#48521

[MarvinGravert]

Hi, I trying myself on this issue: pandas-dev/pandas#35665

[Gramet]

Hi, I'll take pandas-dev/pandas#32218

[ArnaudChanoine]

Hi, I'll kook into pandas-dev/pandas#28871

[PrimeF]

Hi, I'll look into pandas-dev/pandas#5355

[ArnaudChanoine]

Looking into pandas-dev/pandas#33828

[corriebar]

Looking into pandas-dev/pandas#31581

[vagechirkov]

I will take this one pandas-dev/pandas#38147 🙃

[gab50000]

I'll look into pandas-dev/pandas/issues/48238

[MarvinGravert]

Looking into pandas-dev/pandas#29707

[MirijaH]

Looking into: pivot_table produces inconsistent columns if applied to empty table #21932

[oluwatonio]

I'll look into pandas-dev/pandas#44078