Improve test comments under @pytest.mark.parametrize in test_diffraction_objects.py

[bobleesj]

Some battle-tested practices being adopted:

• Replace UC to C
• Add higher-level test function comment before starting "C"
• Use "x, y, z (provided), expect blah blah blah" format for consistency

cc' @yucongalicechen

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.68%. Comparing base (8107874) to head (499a1c3).
Report is 15 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #273 +/- ##
=======================================
Coverage 98.68% 98.68% =======================================
Files 8 8 Lines 379 379 =======================================
Hits 374 374 Misses 5 5 

Files with missing lines	Coverage Δ
tests/test_diffraction_objects.py	100.00% <100.00%> (ø)

[bobleesj]

@sbillinge ready for review.

@yucongalicechen , the part that is remaining is the test_scale_to function.

The existing comments like# C2: Same length x-arrays with exact x-value match, # C3: Same length x-arrays with approximate x-value match were abit hard for me to understand what's being tested. Would you mind improving this test comments for test_scale_to using the above format?

[bobleesj]

(Just added a quick fix) pls see my comments right above

[sbillinge]

please see my comment. I guess this may not be liked by one of our linters or something, but I think I prefer the more compact formatting. Not a huge deal though. Let's just decide which we like and adopt it in future. It is such a small point we don't need to redo things here. Let's dicsus it. But I will merge this.

[sbillinge]

let's not modify this PR again, but I do wonder whether it would be more compact as

 ( # C1: Target value is in the xarray and xtype is identical, expect exact index match
{
"wavelength": 4 * np.pi,
"xarray": np.array([30.005, 60]),
"yarray": np.array([1, 2]),
"xtype": "tth",
},
{
"xtype": "tth",
"value": 30.005,
},
[0],
),

than the current

 # C1: Target value is in the xarray and xtype is identical, expect exact index match
(
{
"wavelength": 4 * np.pi,
"xarray": np.array([30.005, 60]),
"yarray": np.array([1, 2]),
"xtype": "tth",
},
{
"xtype": "tth",
"value": 30.005,
},
[0],
),

[bobleesj]

@sbillinge yeah I like that! The automatic indentation also provides a good visual hierarchy!

[bobleesj]

For single-lined cases, I think we still want to maintain this format right?