Review correctness and simplify tests

[lmmx]

Head overlaps:

• The test for head overlaps seems to be correct but it is too complicated!
• Don’t test positions, test for an exact matching RangeDict (maybe create a fresh one and compare the keys?)
• For example, [3,7) then [2,5) gives: [2,5), [5,7) and [2,5) as the _active_range
  • This is correct! The overlapped range [3,7) is replanted as [5,7)

Tail overlaps:

• There is no test for tail overlaps(?) and it doesn’t seem to be correct
• For example [2,5) then [3,7) gives:
  • an error when trying to access the repr
  • [2,3) and [3,7) in the keys of the internal ranges dict
  • This is correct, and is paired with the correct value, a RangeResponse on [2,5) with tail_mark of 2
  • an error when trying to compute the external ranges dict, arising from compute_external_ranges

I think some new fixtures would help simplify the testing (perhaps even break them out into a module for simplicity?)

[lmmx]

I… don’t think the internal _ranges keys are meant to be different from the RangeResponse range, but they are? And this is the source of the bug in the tail overlap case, which arises when the tail mark gets applied multiple times (once internally, I think in some place where internal and external get mixed up maybe)

This does not happen in the head-overlap case (the _ranges keys match the ranges on the values at those keys in the RangeResponse)

• Makes sense I guess since the tail mark is not applied on head overlaps.
• Doesn’t make sense though as I took care to make a deepcopy and not retain the reference on the internal _ranges, also this was working earlier (the tests did not pick up the regression specifically, arg 🙅)

[lmmx]

I at first suspected the bug is coming from this line:

https://github.com/lmmx/range-streams/blob/56956498cf30ab27820dd2bbd6c64a8c858d24c5/src/range_streams/overlaps.py#L70

I also think that when the test for handle_overlaps stopped working I should have spotted that sign, and not replaced it with a working test(!)

The old test can be found here:

https://github.com/lmmx/range-streams/commit/56956498cf30ab27820dd2bbd6c64a8c858d24c5?branch=56956498cf30ab27820dd2bbd6c64a8c858d24c5&diff=split#diff-5c553c0de613ae24a06f65d61cabb177adf5d727c24a67c6a72975dffa8dbfd5

However note that that test is for overlaps at the head, and the error is arising from an overlap at the tail? So maybe I’m wrong