Refactor test_on_xtype() using @pytest.mark.parametrize and conftest.py

[bobleesj]

Problem

We have 2 PRs opened at the moment, working on the same file.

Once #228 is addressed and merged, refactor:

def test_on_xtype():
    do = DiffractionObject(wavelength=2 * np.pi, xarray=np.array([30, 60]), yarray=np.array([1, 2]), xtype="tth")
    assert np.allclose(do.on_xtype("tth"), [np.array([30, 60]), np.array([1, 2])])
    assert np.allclose(do.on_xtype("2theta"), [np.array([30, 60]), np.array([1, 2])])
    assert np.allclose(do.on_xtype("q"), [np.array([0.51764, 1]), np.array([1, 2])])
    assert np.allclose(do.on_xtype("d"), [np.array([12.13818, 6.28319]), np.array([1, 2])])

Ref: Continuing our in-line comment interactions from #225 (comment)

Proposed solutions

• Use well defined reusable DO instances defined under contest.py