MAINT: Extra test for coreg (#10549)

Author: larsoner

mne/tests/test_coreg.py

@@ -13,7 +13,7 @@
 from mne.datasets import testing
 from mne.transforms import (Transform, apply_trans, rotation, translation,
                             scaling, read_trans, _angle_between_quats,
-                            rot_to_quat)
+                            rot_to_quat, invert_transform)
 from mne.coreg import (fit_matched_points, create_default_subject, scale_mri,
                        _is_mri_subject, scale_labels, scale_source_space,
                        coregister_fiducials, get_mni_fiducials, Coregistration)
@@ -235,6 +235,17 @@ def test_scale_mri_xfm(tmp_path, few_surfaces):
         mni = mne.vertex_to_mni(vertices, hemis, subject_to,
                                 subjects_dir=tempdir)
         assert_allclose(mni, mni_from, atol=1e-3)  # 0.001 mm
+        # Check head_to_mni (the `trans` here does not really matter)
+        trans = rotation(0.001, 0.002, 0.003) @ translation(0.01, 0.02, 0.03)
+        trans = Transform('head', 'mri', trans)
+        pos_head_from = np.random.RandomState(0).randn(4, 3)
+        pos_mni_from = mne.head_to_mni(
+            pos_head_from, subject_from, trans, tempdir)
+        pos_mri_from = apply_trans(trans, pos_head_from)
+        pos_mri = pos_mri_from * scale
+        pos_head = apply_trans(invert_transform(trans), pos_mri)
+        pos_mni = mne.head_to_mni(pos_head, subject_to, trans, tempdir)
+        assert_allclose(pos_mni, pos_mni_from, atol=1e-3)
 
 
 def test_fit_matched_points():