Move tests into tests directory

[graeme-winter]

Kept the structure the same as far as possible. Had to fix references in flight. I think all the tests should pass, will run regression tests in a mo.

Motivation: consistency

[Anthchirp]

If you move the tests into /tests with the aim of eventually removing them from the python package, then __init__.pys should not be moved along, which will also prevent the files from becoming importable. If the tests have import dependencies between them then they need to be rewritten/moved back later, and then it'd be easier to just leave them where they are.

[graeme-winter]

If you move the tests into /tests with the aim of eventually removing them from the python package, then __init__.pys should not be moved along, which will also prevent the files from becoming importable. If the tests have import dependencies between them then they need to be rewritten/moved back later, and then it'd be easier to just leave them where they are.

My motivation is wanting to be able to find the tests easily without needing to use the UNIX find command - future Python package was motivation for renaming test->tests but that is "while I was there"

[graeme-winter]

Hmmm would seem there is a lot of weird crosstalk between tests (i.e. there are tests which are very not self-contained and imported bits of other tests from other folders e.g.

――――――― ERROR collecting tests/command_line/test_search_beam_position.py ―――――――
ImportError while importing test module '/Users/graeme/git/dials/modules/dials/tests/command_line/test_search_beam_position.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
../../conda_base/python.app/Contents/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/command_line/test_search_beam_position.py:11: in <module>
    from dials.algorithms.indexing.test_index import run_indexing
E   ModuleNotFoundError: No module named 'dials.algorithms.indexing.test_index'

which weirdly does not cause test failure)

[Anthchirp]

Collection errors are errors, which are a separate category from test failures. Should still lead to failed builds on Azure

[Anthchirp]

minimal command to reproduce the issue:

pytest doc/examples/test_boilerplate.py::test_boilerplate tests/algorithms/indexing/basis_vector_search/test_combinations.py::test_filter_known_symmetry_no_matches --regression

[codecov]

Codecov Report

Merging #1698 (d6cc25a) into main (f0d524a) will decrease coverage by 0.00%.
The diff coverage is 97.43%.

@@            Coverage Diff             @@
##             main    #1698      +/-   ##
==========================================
- Coverage   67.13%   67.13%   -0.01%     
==========================================
  Files         615      615              
  Lines       69053    69051       -2     
  Branches     9622     9622              
==========================================
- Hits        46356    46354       -2     
+ Misses      20765    20764       -1     
- Partials     1932     1933       +1     

[Anthchirp]

xfel_regression refers to from dials.test.(...) import ... in tst_ensemble_refinement.py, so that is the likely reason for the x_r failure.

But this PR is ready for merging.

[phyy-nx]

I've patched xfel_regression to refer to the new location in tst_ensemble_refinement.py.

[Anthchirp]

Thanks!