Add test on Series.getitem failure

[akharche]

[AlexanderKalistratov]

What is the issue? getitem with negative slice is failing?

[kozlov-alexey]

What is the issue? getitem with negative slice is failing?

@akharche @AlexanderKalistratov The issue here is in the empty slice for the string series index only (other combinations seem to pass), i.e. original test fails on the second iteration, when start=-2, end=0 and index is ['2', '3', '5', '6', '7']. And the resulting slice should be:

a = np.asarray([1, 2, 3, 1, 2, 4, 5])
a[-2:0]
array([], dtype=int32)