diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 5abda71b..03e93c1d 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -110,7 +110,7 @@ jobs:
 
       - name: Run tests
         run: |
-          pytest --pyargs orix --runslow --reruns 2 -n 2 --cov=orix
+          pytest --pyargs orix --slow --reruns 2 -n 2 --cov=orix
 
       - name: Generate line coverage
         if: ${{ matrix.os == 'ubuntu-latest' }}
diff --git a/doc/conf.py b/doc/conf.py
index 2b81c2d3..9dafd02c 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -1,3 +1,22 @@
+#
+# Copyright 2019-2025 the orix developers
+#
+# This file is part of orix.
+#
+# orix is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# orix is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
+
 # Configuration file for the Sphinx documentation app.
 # See the documentation for a full list of configuration options:
 # https://www.sphinx-doc.org/en/master/usage/configuration.html
@@ -64,9 +83,10 @@
     "numpydoc": ("https://numpydoc.readthedocs.io/en/latest", None),
     "pooch": ("https://www.fatiando.org/pooch/latest", None),
     "pytest": ("https://docs.pytest.org/en/stable", None),
+    "pytest-xdist": ("https://pytest-xdist.readthedocs.io/en/stable/", None),
     "python": ("https://docs.python.org/3", None),
     "pyxem": ("https://pyxem.readthedocs.io/en/latest", None),
-    "readthedocs": ("https://docs.readthedocs.io/en/stable", None),
+    "readthedocs": ("https://docs.readthedocs.com/platform/stable/", None),
     "scipy": ("https://docs.scipy.org/doc/scipy", None),
     "sklearn": ("https://scikit-learn.org/stable", None),
     "sphinx": ("https://www.sphinx-doc.org/en/master", None),
diff --git a/doc/dev/running_writing_tests.rst b/doc/dev/running_writing_tests.rst
index ab205cf4..da832cb8 100644
--- a/doc/dev/running_writing_tests.rst
+++ b/doc/dev/running_writing_tests.rst
@@ -3,11 +3,12 @@ Run and write tests
 
 All functionality in orix is tested with :doc:`pytest <pytest:index>`.
 The tests reside in a ``tests`` module.
-Tests are short methods that call functions in ``orix`` and compare resulting output
-values with known answers.
+Tests are short methods that call functions in orix and compare resulting output values
+with known answers.
+
 Install necessary dependencies to run the tests::
 
-   pip install --editable ".[tests]"
+    pip install -e ".[tests]"
 
 Some useful :doc:`fixtures <pytest:explanation/fixtures>` are available in the
 ``conftest.py`` file.
@@ -22,29 +23,28 @@ Some useful :doc:`fixtures <pytest:explanation/fixtures>` are available in the
 
 To run the tests::
 
-  pytest --cov --pyargs orix -n auto
+    pytest --cov --pyargs orix -n auto
 
-The ``-n auto`` is an optional flag to enable parallelized testing. 
-The ``--cov`` flag makes :doc:`coverage.py <coverage:index>` print a nice report.
-For an even nicer presentation, you can use ``coverage.py`` directly::
+The ``-n auto`` is an optional flag to enable parallelized testing with
+:doc:`pytest-xdist <pytest-xdist:index>`.
+We aim to cover all lines when all :ref:`dependencies` are installed.
+The ``--cov`` flag makes :doc:`coverage.py <coverage:index>` print a nice coverage
+report.
+For an even nicer presentation, you can use coverage.py directly::
 
-   coverage html
+    coverage html
 
 Coverage can then be inspected in the browser by opening ``htmlcov/index.html``.
 
-We strive for 100% test coverage of lines when all dependencies are installed.
-
-If you have a test that takes a long time to run, you can mark it to skip it from running by default
-
-.. code-block:: Python
+If a test takes a long time to run, you can mark it to skip it from running by default::
 
     @pytest.mark.slow
     def test_slow_function():
-        pass
+        ...
 
-Then you can run the tests with the ``--runslow`` option to skip slow tests::
+To run tests marked as slow, add the flag when running pytest::
 
-    pytest --runslow
+    pytest --slow
 
 Docstring examples are tested with :doc:`pytest <pytest:how-to/doctest>` as well.
 :mod:`numpy` and :mod:`matplotlib.pyplot` should not be imported in examples as they are
diff --git a/orix/crystal_map/phase_list.py b/orix/crystal_map/phase_list.py
index ff99ee89..ce7e3b91 100644
--- a/orix/crystal_map/phase_list.py
+++ b/orix/crystal_map/phase_list.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,11 +10,12 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 from __future__ import annotations
 
@@ -37,7 +39,8 @@
     _groups,
     get_point_group,
 )
-from orix.vector import Miller, Vector3d
+from orix.vector.miller import Miller
+from orix.vector.vector3d import Vector3d
 
 # All named Matplotlib colors (tableau and xkcd already lower case hex)
 ALL_COLORS = mcolors.TABLEAU_COLORS
@@ -366,18 +369,26 @@ def deepcopy(self) -> Phase:
         return copy.deepcopy(self)
 
     def expand_asymmetric_unit(self) -> Phase:
-        """Return new instance with all symmetrically equivalent atoms.
+        """Return a new phase with all symmetrically equivalent atoms.
+
+        Returns
+        -------
+        expanded_phase
+            New phase with the a :attr:`structure` with the unit cell
+            filled with symmetrically equivalent atoms.
 
         Examples
         --------
+        >>> from diffpy.structure import Atom, Lattice, Structure
+        >>> import orix.crystal_map as ocm
         >>> atoms = [Atom("Si", xyz=(0, 0, 1))]
         >>> lattice = Lattice(4.04, 4.04, 4.04, 90, 90, 90)
         >>> structure = Structure(atoms = atoms,lattice=lattice)
-        >>> phase = Phase(structure=structure, space_group=227)
+        >>> phase = ocm.Phase(structure=structure, space_group=227)
         >>> phase.structure
         [Si   0.000000 0.000000 1.000000 1.0000]
-        >>> expanded = phase.expand_asymmetric_unit()
-        >>> expanded.structure
+        >>> expanded_phase = phase.expand_asymmetric_unit()
+        >>> expanded_phase.structure
         [Si   0.000000 0.000000 0.000000 1.0000,
          Si   0.000000 0.500000 0.500000 1.0000,
          Si   0.500000 0.500000 0.000000 1.0000,
@@ -411,9 +422,10 @@ def expand_asymmetric_unit(self) -> Phase:
                     diffpy_structure.append(new_atom)
 
         # This handles conversion back to correct alignment
-        out = Phase(self)
-        out.structure = diffpy_structure
-        return out
+        expanded_phase = self.__class__(self)
+        expanded_phase.structure = diffpy_structure
+
+        return expanded_phase
 
 
 class PhaseList:
diff --git a/orix/quaternion/quaternion.py b/orix/quaternion/quaternion.py
index 9e0b260d..b0b67730 100644
--- a/orix/quaternion/quaternion.py
+++ b/orix/quaternion/quaternion.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,15 +10,16 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 from __future__ import annotations
 
-from typing import Any, Optional, Tuple, Union
+from typing import Any
 import warnings
 
 import dask.array as da
@@ -29,7 +31,9 @@
 from orix._base import Object3d
 from orix.constants import installed
 from orix.quaternion import _conversions
-from orix.vector import AxAngle, Homochoric, Miller, Rodrigues, Vector3d
+from orix.vector.miller import Miller
+from orix.vector.neo_euler import AxAngle, Homochoric, Rodrigues
+from orix.vector.vector3d import Vector3d
 
 
 class Quaternion(Object3d):
@@ -193,9 +197,7 @@ def conj(self) -> Quaternion:
     def __invert__(self) -> Quaternion:
         return self.__class__(self.conj.data / (self.norm**2)[..., np.newaxis])
 
-    def __mul__(
-        self, other: Union[Quaternion, Vector3d]
-    ) -> Union[Quaternion, Vector3d]:
+    def __mul__(self, other: Quaternion | Vector3d) -> Quaternion | Vector3d:
         if isinstance(other, Quaternion):
             if installed["numpy-quaternion"]:
                 import quaternion
@@ -231,7 +233,7 @@ def __mul__(
     def __neg__(self) -> Quaternion:
         return self.__class__(-self.data)
 
-    def __eq__(self, other: Union[Any, Quaternion]) -> bool:
+    def __eq__(self, other: Any | Quaternion) -> bool:
         """Check if quaternions have equal shapes and components."""
         if (
             isinstance(other, Quaternion)
@@ -247,8 +249,8 @@ def __eq__(self, other: Union[Any, Quaternion]) -> bool:
     @classmethod
     def from_axes_angles(
         cls,
-        axes: Union[np.ndarray, Vector3d, tuple, list],
-        angles: Union[np.ndarray, tuple, list, float],
+        axes: np.ndarray | Vector3d | tuple | list,
+        angles: np.ndarray | tuple | list | float,
         degrees: bool = False,
     ) -> Quaternion:
         r"""Create unit quaternions from axis-angle pairs
@@ -299,8 +301,7 @@ def from_axes_angles(
 
     @classmethod
     def from_homochoric(
-        cls,
-        ho: Union[Vector3d, Homochoric, np.ndarray, tuple, list],
+        cls, ho: Vector3d | Homochoric | np.ndarray | tuple | list
     ) -> Quaternion:
         r"""Create unit quaternions from homochoric vectors
         :math:`\mathbf{h}` :cite:`rowenhorst2015consistent`.
@@ -346,8 +347,8 @@ def from_homochoric(
     @classmethod
     def from_rodrigues(
         cls,
-        ro: Union[np.ndarray, Vector3d, tuple, list],
-        angles: Union[np.ndarray, tuple, list, float, None] = None,
+        ro: np.ndarray | Vector3d | tuple | list,
+        angles: np.ndarray | tuple | list | float | None = None,
     ) -> Quaternion:
         r"""Create unit quaternions from three-component Rodrigues
         vectors :math:`\hat{\mathbf{n}}` or four-component
@@ -448,7 +449,7 @@ def from_rodrigues(
     @classmethod
     def from_euler(
         cls,
-        euler: Union[np.ndarray, tuple, list],
+        euler: np.ndarray | tuple | list,
         direction: str = "lab2crystal",
         degrees: bool = False,
     ) -> Quaternion:
@@ -505,7 +506,7 @@ def from_euler(
         return Q
 
     @classmethod
-    def from_matrix(cls, matrix: Union[np.ndarray, tuple, list]) -> Quaternion:
+    def from_matrix(cls, matrix: np.ndarray | tuple | list) -> Quaternion:
         """Create unit quaternions from orientation matrices
         :cite:`rowenhorst2015consistent`.
 
@@ -552,9 +553,13 @@ def from_scipy_rotation(cls, rotation: SciPyRotation) -> Quaternion:
 
         Returns
         -------
-        quaternion
+        Q
             Quaternions.
 
+        See Also
+        --------
+        to_scipy_rotation
+
         Notes
         -----
         The SciPy rotation is inverted to be consistent with the orix
@@ -600,17 +605,17 @@ def from_scipy_rotation(cls, rotation: SciPyRotation) -> Quaternion:
     @classmethod
     def from_align_vectors(
         cls,
-        other: Union[Vector3d, tuple, list],
-        initial: Union[Vector3d, tuple, list],
-        weights: Optional[np.ndarray] = None,
+        other: Vector3d | tuple | list,
+        initial: Vector3d | tuple | list,
+        weights: np.ndarray | None = None,
         return_rmsd: bool = False,
         return_sensitivity: bool = False,
-    ) -> Union[
-        Quaternion,
-        Tuple[Quaternion, float],
-        Tuple[Quaternion, np.ndarray],
-        Tuple[Quaternion, float, np.ndarray],
-    ]:
+    ) -> (
+        Quaternion
+        | tuple[Quaternion, float]
+        | tuple[Quaternion, np.ndarray]
+        | tuple[Quaternion, float, np.ndarray]
+    ):
         """Estimate a quaternion to optimally align two sets of vectors.
 
         This method wraps
@@ -739,7 +744,7 @@ def triple_cross(cls, q1: Quaternion, q2: Quaternion, q3: Quaternion) -> Quatern
         return Q
 
     @classmethod
-    def identity(cls, shape: Union[int, tuple] = (1,)) -> Quaternion:
+    def identity(cls, shape: int | tuple = (1,)) -> Quaternion:
         """Create identity quaternions.
 
         Parameters
@@ -836,7 +841,7 @@ def to_axes_angles(self) -> AxAngle:
         ax = AxAngle(axes * angles)
         return ax
 
-    def to_rodrigues(self, frank: bool = False) -> Union[Rodrigues, np.ndarray]:
+    def to_rodrigues(self, frank: bool = False) -> Rodrigues | np.ndarray:
         r"""Return the unit quaternions as Rodrigues or Rodrigues-Frank
          vectors :cite:`rowenhorst2015consistent`.
 
@@ -946,45 +951,44 @@ def to_homochoric(self) -> Homochoric:
         return ho
 
     def to_scipy_rotation(self) -> SciPyRotation:
-        r"""Return the unit quaternions as
-        :class:`scipy.spatial.transform.Rotation` objects used in scipy's
-        spatial module.
+        r"""Return unit quaternions as a SciPy rotation.
 
         Returns
         -------
-        SciPy_Rotation
-            a Rotation object generated from the unit quaternion data
-            (i.e, unaffected by symmetry, phase, or length).
+        scipy_rotation
+            A SciPy rotation (flattened) given by the unit quaternions
+            without considering any symmetry.
+
+        See Also
+        --------
+        from_scipy_rotation
 
         Notes
         -----
-        SciPy by default uses the Active rotation convention along with the
-        vector-scalar quaternion definition, as opposed to ORIX's passive,
-        scalar-vector convention. Thus, the following quaternion in orix:
-        :math: `q_{orix} = [q_0, q_1, q_2, q_3]`
-        represents the same operations as the following quaternion in scipy:
-        :math: `q_{SciPy} = [-q_1, -q_2, -q_3, q_0]`
-
-        See the function description for Quaternion.from_scipy_rotation
-        for an example of how these differing parameterizations still produce
-        identical rotation operations.
-
-        Additionally, note that Orix enforces :math: `q_0 >= 0` whereas
-        SciPy does not. Thus, the operation
-
-        >>> Quaternion.from_scipy_rotation(r).to_scipy_rotation.as_quat()
-
-        will produce an identical rotation operation, but not
-        necessarily an idential quaternion. Look up "quaternion double cover"
-        for more information on why this occurs.
-
-        Finally, ORIX supports N-dimensional arrays, whereas SciPy
-        currently supports only 1-dimensional vectors. Thus, this function
-        will also flatten arrays when converting to SciPy Rotations.
+        SciPy by default uses the active rotation interpretation along
+        with the vector-scalar quaternion definition, as opposed to
+        orix's passive one, scalar-vector interpretation. Thus, the
+        following quaternion in orix,
+        :math:`Q_{orix} = [q_0, q_1, q_2, q_3]` represents the same
+        transformation as the following quaternion in SciPy:
+        :math:`Q_{SciPy} = [-q_1, -q_2, -q_3, q_0]`
+
+        See the function description for :meth:`from_scipy_rotation` for
+        an example of how these differing parameterizations still
+        produce identical transformations.
+
+        Additionally, note that orix enforces :math:`Q_0 \geq 0` whereas
+        SciPy does not. Thus, the operation::
+
+            Quaternion.from_scipy_rotation(r).to_scipy_rotation.as_quat()
+
+        will produce an identical transformation, but not necessarily an
+        idential quaternion. Look up "quaternion double cover" for more
+        information on why this occurs.
         """
         if self.ndim > 1:
             warnings.warn(
-                "\n    {} dimension greater than 1. ".format(self.__class__.__name__)
+                f"\n    {self.__class__.__name__} dimension greater than 1. "
                 + "Flattening into a 1-dimensional vector"
             )
             self = self.flatten()
@@ -1075,11 +1079,11 @@ def mean(self) -> Quaternion:
 
     def outer(
         self,
-        other: Union[Quaternion, Vector3d],
+        other: Quaternion | Vector3d,
         lazy: bool = False,
         chunk_size: int = 20,
         progressbar: bool = True,
-    ) -> Union[Quaternion, Vector3d]:
+    ) -> Quaternion | Vector3d:
         """Return the outer products of the quaternions and the other
         quaternions or vectors.
 
@@ -1171,7 +1175,7 @@ def inv(self) -> Quaternion:
     # -------------------- Other private methods --------------------- #
 
     def _outer_dask(
-        self, other: Union[Quaternion, Vector3d], chunk_size: int = 20
+        self, other: Quaternion | Vector3d, chunk_size: int = 20
     ) -> da.Array:
         """Compute the product of every quaternion in this instance to
         every quaternion or vector in another instance, returned as a
diff --git a/orix/quaternion/rotation.py b/orix/quaternion/rotation.py
index 64ce43e8..811f79a0 100644
--- a/orix/quaternion/rotation.py
+++ b/orix/quaternion/rotation.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,23 +10,24 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 from __future__ import annotations
 
-from typing import Any, Tuple, Union
+from typing import Any
 
 import dask.array as da
 from dask.diagnostics import ProgressBar
 import numpy as np
 from scipy.special import hyp0f1
 
-from orix.quaternion import Quaternion
-from orix.vector import Vector3d
+from orix.quaternion.quaternion import Quaternion
+from orix.vector.vector3d import Vector3d
 
 
 class Rotation(Quaternion):
@@ -73,7 +75,7 @@ class Rotation(Quaternion):
     True
     """
 
-    def __init__(self, data: Union[np.ndarray, Rotation, list, tuple]):
+    def __init__(self, data: np.ndarray | Rotation | list | tuple) -> None:
         super().__init__(data)
         self._data = np.concatenate((self.data, np.zeros(self.shape + (1,))), axis=-1)
         if isinstance(data, Rotation):
@@ -104,8 +106,8 @@ def antipodal(self) -> Rotation:
     # ------------------------ Dunder methods ------------------------ #
 
     def __mul__(
-        self, other: Union[Rotation, Quaternion, Vector3d, np.ndarray, int, list]
-    ):
+        self, other: Rotation | Quaternion | Vector3d | np.ndarray | int | list
+    ) -> Rotation | Quaternion | Vector3d:
         # Combine rotations self * other as first other, then self
         if isinstance(other, Rotation):
             Q = Quaternion(self) * Quaternion(other)
@@ -146,7 +148,7 @@ def __invert__(self) -> Rotation:
         R.improper = self.improper
         return R
 
-    def __eq__(self, other: Union[Any, Rotation]) -> bool:
+    def __eq__(self, other: Any | Rotation) -> bool:
         """Check if the rotations have equal shapes and values."""
         if (
             isinstance(other, Rotation)
@@ -163,9 +165,9 @@ def __eq__(self, other: Union[Any, Rotation]) -> bool:
     @classmethod
     def random_vonmises(
         cls,
-        shape: Union[int, tuple] = (1,),
+        shape: int | tuple = (1,),
         alpha: float = 1.0,
-        reference: Union[list, tuple, Rotation] = (1, 0, 0, 0),
+        reference: Rotation | list | tuple = (1, 0, 0, 0),
     ) -> Rotation:
         """Return random rotations with a simplified Von Mises-Fisher
         distribution.
@@ -206,11 +208,9 @@ def unique(
         return_index: bool = False,
         return_inverse: bool = False,
         antipodal: bool = True,
-    ) -> Union[
-        Rotation,
-        Tuple[Rotation, np.ndarray],
-        Tuple[Rotation, np.ndarray, np.ndarray],
-    ]:
+    ) -> (
+        Rotation | tuple[Rotation, np.ndarray] | tuple[Rotation, np.ndarray, np.ndarray]
+    ):
         """Return the unique rotations from these rotations.
 
         Two rotations are not unique if they have the same propriety
@@ -343,11 +343,11 @@ def angle_with_outer(self, other: Rotation, degrees: bool = False) -> np.ndarray
 
     def outer(
         self,
-        other: Union[Rotation, Vector3d],
+        other: Rotation | Vector3d,
         lazy: bool = False,
         chunk_size: int = 20,
         progressbar: bool = True,
-    ) -> Union[Rotation, Vector3d]:
+    ) -> Rotation | Vector3d:
         """Return the outer rotation products of the rotations and the
         other rotations or vectors.
 
diff --git a/orix/quaternion/symmetry.py b/orix/quaternion/symmetry.py
index ec3061ef..417f04ad 100644
--- a/orix/quaternion/symmetry.py
+++ b/orix/quaternion/symmetry.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,11 +10,12 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 from __future__ import annotations
 
@@ -24,11 +26,11 @@
 import numpy as np
 
 from orix.quaternion.rotation import Rotation
-from orix.vector import Vector3d
+from orix.vector.vector3d import Vector3d
 
 if TYPE_CHECKING:  # pragma: no cover
-    from orix.quaternion import Orientation
-    from orix.vector import FundamentalSector
+    from orix.quaternion.orientation import Orientation
+    from orix.vector.fundamental_sector import FundamentalSector
 
 
 class Symmetry(Rotation):
diff --git a/orix/tests/conftest.py b/orix/tests/conftest.py
index 7684e6d6..6852fd3d 100644
--- a/orix/tests/conftest.py
+++ b/orix/tests/conftest.py
@@ -16,80 +16,64 @@
 # You should have received a copy of the GNU General Public License
 # along with orix. If not, see <http://www.gnu.org/licenses/>.
 #
-
-
-import os
-from tempfile import TemporaryDirectory
-
 from diffpy.structure import Atom, Lattice, Structure
 from h5py import File
 import matplotlib.pyplot as plt
 import numpy as np
 import pytest
 
-from orix import constants
-from orix.crystal_map import CrystalMap, PhaseList, create_coordinate_arrays
-from orix.quaternion import Rotation
+from orix.constants import installed
+from orix.crystal_map.crystal_map import CrystalMap, create_coordinate_arrays
+from orix.crystal_map.phase_list import PhaseList
+from orix.quaternion.rotation import Rotation
 
 # --------------------------- pytest hooks --------------------------- #
 
 
-def pytest_sessionstart(session):  # pragma: no cover
+def pytest_sessionstart(session):
     plt.rcParams["backend"] = "agg"
 
 
 # -------------------- Control of test selection --------------------- #
 
 skipif_numpy_quaternion_present = pytest.mark.skipif(
-    constants.installed["numpy-quaternion"], reason="numpy-quaternion installed"
+    installed["numpy-quaternion"], reason="numpy-quaternion installed"
 )
 
 skipif_numpy_quaternion_missing = pytest.mark.skipif(
-    not constants.installed["numpy-quaternion"], reason="numpy-quaternion not installed"
+    not installed["numpy-quaternion"], reason="numpy-quaternion not installed"
 )
 
-# ---------------------------- IO fixtures --------------------------- #
-
-# ----------------------------- .ang file ---------------------------- #
-
 
 def pytest_addoption(parser):
     parser.addoption(
-        "--runslow", action="store_true", default=False, help="run slow tests"
+        "--slow", action="store_true", default=False, help="Run slow tests"
     )
 
 
-def pytest_configure(config):
-    config.addinivalue_line("markers", "slow: mark test as slow to run")
+# Markers are defined in package configuration
+MARKERS = ["slow"]
 
 
-def pytest_collection_modifyitems(config, items):
-    if config.getoption("--runslow"):
-        # --runslow given in cli: do not skip slow tests
-        return
-    else:  # pragma: no cover
-        skip_slow = pytest.mark.skip(reason="need --runslow option to run")
-        for item in items:
-            if "slow" in item.keywords:
-                item.add_marker(skip_slow)
+def pytest_runtest_setup(item):
+    # Skip certain tests when flag is missing:
+    # https://docs.pytest.org/en/stable/reference/reference.html#pytest.hookspec.pytest_runtest_setup
+    for marker in MARKERS:
+        marker_str = f"--{marker}"
+        if marker in item.keywords and not item.config.getoption(marker_str):
+            pytest.skip(f"Needs {marker_str} flag to run")
 
 
-@pytest.fixture()
-def temp_ang_file():
-    with TemporaryDirectory() as tempdir:
-        f = open(os.path.join(tempdir, "temp_ang_file.ang"), mode="w+")
-        yield f
+# ---------------------------- IO fixtures --------------------------- #
 
+# ----------------------------- .ang file ---------------------------- #
 
-@pytest.fixture(params=["h5"])
-def temp_file_path(request):
-    """Temporary file in a temporary directory for use when tests need
-    to write, and sometimes read again, data to, and from, a file.
-    """
-    ext = request.param
-    with TemporaryDirectory() as tmp:
-        file_path = os.path.join(tmp, "data_temp." + ext)
-        yield file_path
+
+@pytest.fixture()
+def temp_ang_file(tmpdir):
+    fname = tmpdir.join("temp_ang_file.ang")
+    with open(fname, mode="w+") as f:
+        yield f
 
 
 ANGFILE_TSL_HEADER = r"""# TEM_PIXperUM          1.000000
@@ -392,7 +376,7 @@ def angfile_emsoft(tmpdir, request):
 # Variable map shape and step sizes
 CTF_OXFORD_HEADER = r"""Channel Text File
 Prj	standard steel sample
-Author	
+Author
 JobMode	Grid
 XCells	%i
 YCells	%i
@@ -754,7 +738,7 @@ def ctf_emsoft(tmpdir, request):
 AcqE1	0.0000
 AcqE2	0.0000
 AcqE3	0.0000
-Euler angles refer to Sample Coordinate system (CS0)!	Mag	0.0000	Coverage	0	Device	0	KV	0.0000	TiltAngle	0.0000	TiltAxis	0	DetectorOrientationE1	0.0000	DetectorOrientationE2	0.0000	DetectorOrientationE3	0.0000	WorkingDistance	0.0000	InsertionDistance	0.0000	
+Euler angles refer to Sample Coordinate system (CS0)!	Mag	0.0000	Coverage	0	Device	0	KV	0.0000	TiltAngle	0.0000	TiltAxis	0	DetectorOrientationE1	0.0000	DetectorOrientationE2	0.0000	DetectorOrientationE3	0.0000	WorkingDistance	0.0000	InsertionDistance	0.0000
 Phases	1
 4.079;4.079;4.079	90.000;90.000;90.000	Gold	11	0			Created from mtex
 Phase	X	Y	Bands	Error	Euler1	Euler2	Euler3	MAD	BC	BS"""
diff --git a/orix/tests/io/test_ang.py b/orix/tests/io/test_ang.py
index b224bfda..f1f57e78 100644
--- a/orix/tests/io/test_ang.py
+++ b/orix/tests/io/test_ang.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,11 +10,12 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 import numpy as np
 import pytest
@@ -371,23 +373,24 @@ def test_load_ang_emsoft(
     def test_get_header(self, temp_ang_file):
         temp_ang_file.write(ANGFILE_ASTAR_HEADER)
         temp_ang_file.close()
-        assert _get_header(open(temp_ang_file.name)) == [
-            "# File created from ACOM RES results",
-            "# ni-dislocations.res",
-            "#     ".rstrip(),
-            "#     ".rstrip(),
-            "# MaterialName      Nickel",
-            "# Formula",
-            "# Symmetry          43",
-            "# LatticeConstants  3.520  3.520  3.520  90.000  90.000  90.000",
-            "# NumberFamilies    4",
-            "# hklFamilies       1  1  1 1 0.000000",
-            "# hklFamilies       2  0  0 1 0.000000",
-            "# hklFamilies       2  2  0 1 0.000000",
-            "# hklFamilies       3  1  1 1 0.000000",
-            "#",
-            "# GRID: SqrGrid#",
-        ]
+        with open(temp_ang_file.name) as f:
+            assert _get_header(f) == [
+                "# File created from ACOM RES results",
+                "# ni-dislocations.res",
+                "#     ".rstrip(),
+                "#     ".rstrip(),
+                "# MaterialName      Nickel",
+                "# Formula",
+                "# Symmetry          43",
+                "# LatticeConstants  3.520  3.520  3.520  90.000  90.000  90.000",
+                "# NumberFamilies    4",
+                "# hklFamilies       1  1  1 1 0.000000",
+                "# hklFamilies       2  0  0 1 0.000000",
+                "# hklFamilies       2  2  0 1 0.000000",
+                "# hklFamilies       3  1  1 1 0.000000",
+                "#",
+                "# GRID: SqrGrid#",
+            ]
 
     @pytest.mark.parametrize(
         "expected_vendor, expected_columns, vendor_header",
@@ -419,7 +422,8 @@ def test_get_vendor_columns(
 
         temp_ang_file.write(vendor_header)
         temp_ang_file.close()
-        header = _get_header(open(temp_ang_file.name))
+        with open(temp_ang_file.name) as f:
+            header = _get_header(f)
         vendor, column_names = _get_vendor_columns(header, n_cols_file)
 
         assert vendor == expected_vendor
@@ -429,7 +433,8 @@ def test_get_vendor_columns(
     def test_get_vendor_columns_unknown(self, temp_ang_file, n_cols_file):
         temp_ang_file.write("Look at me!\nI'm Mr. .ang file!\n")
         temp_ang_file.close()
-        header = _get_header(open(temp_ang_file.name))
+        with open(temp_ang_file.name) as f:
+            header = _get_header(f)
         with pytest.warns(UserWarning, match=f"Number of columns, {n_cols_file}, "):
             vendor, column_names = _get_vendor_columns(header, n_cols_file)
             assert vendor == "unknown"
diff --git a/orix/tests/io/test_h5ebsd.py b/orix/tests/io/test_h5ebsd.py
index c364e71a..b309bbec 100644
--- a/orix/tests/io/test_h5ebsd.py
+++ b/orix/tests/io/test_h5ebsd.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,11 +10,12 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 from h5py import File
 
@@ -22,12 +24,13 @@
 
 
 class TestH5ebsd:
-    def test_hdf5group2dict_update_dict(self, temp_file_path, crystal_map):
+    def test_hdf5group2dict_update_dict(self, tmp_path, crystal_map):
         """Can read datasets from an HDF5 file into an existing
         dictionary.
         """
-        save(temp_file_path, crystal_map)
-        with File(temp_file_path, mode="r") as f:
+        fname = tmp_path / "test.h5"
+        save(fname, crystal_map)
+        with File(fname, mode="r") as f:
             this_dict = {"hello": "there"}
             this_dict = hdf5group2dict(f["crystal_map"], dictionary=this_dict)
             assert this_dict["hello"] == "there"
diff --git a/orix/tests/io/test_io.py b/orix/tests/io/test_io.py
index fe276927..46258910 100644
--- a/orix/tests/io/test_io.py
+++ b/orix/tests/io/test_io.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,11 +10,12 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 from collections import OrderedDict
 from contextlib import contextmanager
@@ -73,11 +75,11 @@ def test_load_no_filename_match(self):
         with pytest.raises(IOError, match=f"No filename matches '{fname}'."):
             _ = load(fname)
 
-    @pytest.mark.parametrize("temp_file_path", ["ktf"], indirect=["temp_file_path"])
-    def test_load_unsupported_format(self, temp_file_path):
-        np.savetxt(temp_file_path, X=np.random.rand(100, 8))
-        with pytest.raises(IOError, match=f"Could not read "):
-            _ = load(temp_file_path)
+    def test_load_unsupported_format(self, tmp_path):
+        fname = tmp_path / "unsupported_file.ktf"
+        np.savetxt(fname, X=np.random.rand(100, 8))
+        with pytest.raises(IOError, match="Could not read "):
+            _ = load(fname)
 
     @pytest.mark.parametrize(
         "manufacturer, expected_plugin",
@@ -88,61 +90,62 @@ def test_load_unsupported_format(self, temp_file_path):
             ("Oxford", None),
         ],
     )
-    def test_plugin_from_manufacturer(
-        self, temp_file_path, manufacturer, expected_plugin
-    ):
+    def test_plugin_from_manufacturer(self, manufacturer, expected_plugin, tmp_path):
         h5ebsd_plugin_list = [bruker_h5ebsd, emsoft_h5ebsd, orix_hdf5]
-        with File(temp_file_path, mode="w") as f:
+        fname = tmp_path / "test.h5"
+        with File(fname, mode="w") as f:
             f.create_dataset(name="Manufacturer", data=manufacturer)
             assert (
-                _plugin_from_manufacturer(temp_file_path, plugins=h5ebsd_plugin_list)
+                _plugin_from_manufacturer(fname, plugins=h5ebsd_plugin_list)
                 is expected_plugin
             )
 
-    def test_overwrite_or_not(self, crystal_map, temp_file_path):
-        save(temp_file_path, crystal_map)
+    def test_overwrite_or_not(self, crystal_map, tmp_path):
+        fname = tmp_path / "test.h5"
+        save(fname, crystal_map)
         with pytest.warns(UserWarning, match="Not overwriting, since your terminal "):
-            _overwrite_or_not(temp_file_path)
+            _overwrite_or_not(fname)
 
     @pytest.mark.parametrize(
         "answer, expected", [("y", True), ("n", False), ("m", None)]
     )
-    def test_overwrite_or_not_input(
-        self, crystal_map, temp_file_path, answer, expected
-    ):
-        save(temp_file_path, crystal_map)
+    def test_overwrite_or_not_input(self, crystal_map, answer, expected, tmp_path):
+        fname = tmp_path / "test.h5"
+        save(fname, crystal_map)
         if answer == "m":
             with replace_stdin(StringIO(answer)):
                 with pytest.raises(EOFError):
-                    _overwrite_or_not(temp_file_path)
+                    _overwrite_or_not(fname)
         else:
             with replace_stdin(StringIO(answer)):
-                assert _overwrite_or_not(temp_file_path) is expected
+                assert _overwrite_or_not(fname) is expected
 
-    @pytest.mark.parametrize("temp_file_path", ["angs", "hdf4", "h6"])
-    def test_save_unsupported_raises(self, temp_file_path, crystal_map):
-        _, ext = os.path.splitext(temp_file_path)
+    @pytest.mark.parametrize("ext", ["angs", "hdf4", "h6"])
+    def test_save_unsupported_raises(self, ext, crystal_map, tmp_path):
+        fname = tmp_path / f"test.{ext}"
         with pytest.raises(IOError, match=f"'{ext}' does not correspond to any "):
-            save(temp_file_path, crystal_map)
+            save(fname, crystal_map)
 
-    def test_save_overwrite_raises(self, temp_file_path, crystal_map):
+    def test_save_overwrite_raises(self, crystal_map, tmp_path):
         with pytest.raises(ValueError, match="`overwrite` parameter can only be "):
-            save(temp_file_path, crystal_map, overwrite=1)
+            save(tmp_path / "test.h5", crystal_map, overwrite=1)
 
     @pytest.mark.parametrize(
         "overwrite, expected_phase_name", [(True, "hepp"), (False, "")]
     )
     def test_save_overwrite(
-        self, temp_file_path, crystal_map, overwrite, expected_phase_name
+        self, crystal_map, overwrite, expected_phase_name, tmp_path
     ):
+        fname = tmp_path / "test.h5"
+
         assert crystal_map.phases[0].name == ""
-        save(temp_file_path, crystal_map)
-        assert os.path.isfile(temp_file_path) is True
+        save(fname, crystal_map)
+        assert os.path.isfile(fname) is True
 
         crystal_map.phases[0].name = "hepp"
-        save(temp_file_path, crystal_map, overwrite=overwrite)
+        save(fname, crystal_map, overwrite=overwrite)
 
-        crystal_map2 = load(temp_file_path)
+        crystal_map2 = load(fname)
         assert crystal_map2.phases[0].name == expected_phase_name
 
 
diff --git a/orix/tests/io/test_orix_hdf5.py b/orix/tests/io/test_orix_hdf5.py
index 11796600..8640788c 100644
--- a/orix/tests/io/test_orix_hdf5.py
+++ b/orix/tests/io/test_orix_hdf5.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,11 +10,12 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 from diffpy.structure.spacegroups import GetSpaceGroup
 from h5py import File
@@ -22,7 +24,7 @@
 
 from orix import __version__ as orix_version
 from orix.crystal_map import CrystalMap, Phase
-from orix.io import load, save
+import orix.io as oio
 from orix.io.plugins.orix_hdf5 import (
     atom2dict,
     crystalmap2dict,
@@ -42,10 +44,12 @@
 
 
 class TestOrixHDF5Plugin:
-    def test_file_writer(self, crystal_map, temp_file_path):
-        save(filename=temp_file_path, object2write=crystal_map)
+    def test_file_writer(self, crystal_map, tmp_path):
+        fname = tmp_path / "test.h5"
+
+        oio.save(filename=fname, object2write=crystal_map)
 
-        with File(temp_file_path) as f:
+        with File(fname) as f:
             assert f["manufacturer"][()][0].decode() == "orix"
             assert f["version"][()][0].decode() == orix_version
 
@@ -57,10 +61,12 @@ def test_file_writer(self, crystal_map, temp_file_path):
         ],
         indirect=["crystal_map_input"],
     )
-    def test_write_read_masked(self, crystal_map_input, temp_file_path):
+    def test_write_read_masked(self, crystal_map_input, tmp_path):
+        fname = tmp_path / "test.h5"
+
         xmap = CrystalMap(**crystal_map_input)
-        save(filename=temp_file_path, object2write=xmap[xmap.x > 2])
-        xmap2 = load(temp_file_path)
+        oio.save(filename=fname, object2write=xmap[xmap.x > 2])
+        xmap2 = oio.load(fname)
 
         assert xmap2.size != xmap.size
         with pytest.raises(ValueError, match="operands could not be broadcast"):
@@ -70,13 +76,14 @@ def test_write_read_masked(self, crystal_map_input, temp_file_path):
         assert xmap2.size == xmap.size
         assert np.allclose(xmap2.x, xmap.x)
 
-    def test_file_writer_raises(self, temp_file_path, crystal_map):
+    def test_file_writer_raises(self, crystal_map, tmp_path):
+        fname = tmp_path / "test.h5"
         with pytest.raises(OSError, match="Cannot write to the already open file "):
-            with File(temp_file_path, mode="w") as _:
-                save(temp_file_path, crystal_map, overwrite=True)
+            with File(fname, mode="w") as _:
+                oio.save(fname, crystal_map, overwrite=True)
 
-    def test_dict2hdf5group(self, temp_file_path):
-        with File(temp_file_path, mode="w") as f:
+    def test_dict2hdf5group(self, tmp_path):
+        with File(tmp_path / "test.h5", mode="w") as f:
             group = f.create_group(name="a_group")
             with pytest.warns(UserWarning, match="The orix HDF5 writer could not"):
                 dict2hdf5group(
@@ -141,9 +148,11 @@ def test_structure2dict(self, phase_list):
         assert np.allclose(lattice1["baserot"], lattice2["baserot"])
         assert_dictionaries_are_equal(structure_dict["atoms"], this_dict["atoms"])
 
-    def test_file_reader(self, crystal_map, temp_file_path):
-        save(filename=temp_file_path, object2write=crystal_map)
-        xmap2 = load(filename=temp_file_path)
+    def test_file_reader(self, crystal_map, tmp_path):
+        fname = tmp_path / "test.h5"
+
+        oio.save(filename=fname, object2write=crystal_map)
+        xmap2 = oio.load(filename=fname)
         assert_dictionaries_are_equal(crystal_map.__dict__, xmap2.__dict__)
 
     def test_dict2crystalmap(self, crystal_map):
@@ -207,7 +216,7 @@ def test_dict2atom(self, phase_list):
         assert str(atom.element) == str(atom2.element)
         assert np.allclose(atom.xyz, atom2.xyz)
 
-    def test_write_read_nd_crystalmap_properties(self, temp_file_path, crystal_map):
+    def test_write_read_nd_crystalmap_properties(self, crystal_map, tmp_path):
         """Crystal map properties with more than one value in each point
         (e.g. top matching scores from dictionary indexing) can be written
         and read from file correctly.
@@ -225,8 +234,9 @@ def test_write_read_nd_crystalmap_properties(self, temp_file_path, crystal_map):
         prop3d = np.arange(map_size * 4).reshape(prop3d_shape)
         xmap.prop[prop3d_name] = prop3d
 
-        save(filename=temp_file_path, object2write=xmap)
-        xmap2 = load(temp_file_path)
+        fname = tmp_path / "test.h5"
+        oio.save(filename=fname, object2write=xmap)
+        xmap2 = oio.load(fname)
 
         assert np.allclose(xmap2.prop[prop2d_name], xmap.prop[prop2d_name])
         assert np.allclose(xmap2.prop[prop3d_name], xmap.prop[prop3d_name])
diff --git a/orix/vector/miller.py b/orix/vector/miller.py
index 897898ce..2511a95a 100644
--- a/orix/vector/miller.py
+++ b/orix/vector/miller.py
@@ -1,4 +1,5 @@
-# Copyright 2018-2024 the orix developers
+#
+# Copyright 2019-2025 the orix developers
 #
 # This file is part of orix.
 #
@@ -9,11 +10,12 @@
 #
 # orix is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with orix.  If not, see <http://www.gnu.org/licenses/>.
+# along with orix. If not, see <http://www.gnu.org/licenses/>.
+#
 
 from __future__ import annotations
 
@@ -21,12 +23,6 @@
 from itertools import product
 from typing import TYPE_CHECKING, Optional, Tuple, Union
 
-try:
-    # New in Python 3.11
-    from typing import Self
-except ImportError:  # pragma: no cover
-    from typing_extensions import Self
-
 from diffpy.structure import Lattice
 import numpy as np
 
@@ -344,7 +340,7 @@ def is_hexagonal(self) -> bool:
         return self.phase.is_hexagonal
 
     @property
-    def unit(self) -> Self:
+    def unit(self) -> Miller:
         """Return unit vectors."""
         m = self.__class__(xyz=super().unit.data, phase=self.phase)
         m.coordinate_format = self.coordinate_format
@@ -363,7 +359,7 @@ def __repr__(self) -> str:
             f"{name} {shape}, point group {symmetry}, {coordinate_format}\n" f"{data}"
         )
 
-    def __getitem__(self, key) -> Self:
+    def __getitem__(self, key) -> Miller:
         """NumPy fancy indexing of vectors."""
         m = self.__class__(xyz=self.data[key], phase=self.phase).deepcopy()
         m.coordinate_format = self.coordinate_format
@@ -378,7 +374,7 @@ def from_highest_indices(
         uvw: Union[np.ndarray, list, tuple, None] = None,
         hkl: Union[np.ndarray, list, tuple, None] = None,
         include_zero_vector: bool = False,
-    ) -> Self:
+    ) -> Miller:
         """Create a set of unique direct or reciprocal lattice vectors
         from three highest indices and a phase (crystal lattice and
         symmetry).
@@ -405,7 +401,7 @@ def from_highest_indices(
         return cls(**init_kw).unique()
 
     @classmethod
-    def from_min_dspacing(cls, phase: "Phase", min_dspacing: float = 0.05) -> Self:
+    def from_min_dspacing(cls, phase: "Phase", min_dspacing: float = 0.05) -> Miller:
         """Create a set of unique reciprocal lattice vectors with a
         a direct space interplanar spacing greater than a lower
         threshold.
@@ -432,7 +428,7 @@ def random(
         phase: "Phase",
         shape: Union[int, tuple] = 1,
         coordinate_format: str = "xyz",
-    ) -> Self:
+    ) -> Miller:
         """Create random Miller indices.
 
         Parameters
@@ -466,11 +462,11 @@ def random(
 
     # --------------------- Other public methods --------------------- #
 
-    def deepcopy(self) -> Self:
+    def deepcopy(self) -> Miller:
         """Return a deepcopy of the instance."""
         return deepcopy(self)
 
-    def round(self, max_index: int = 20) -> Self:
+    def round(self, max_index: int = 20) -> Miller:
         """Round a set of index triplet (Miller) or quartet
         (Miller-Bravais/Weber) to the *closest* smallest integers.
 
@@ -498,7 +494,9 @@ def symmetrise(
         unique: bool = False,
         return_multiplicity: bool = False,
         return_index: bool = False,
-    ) -> Union[Self, Tuple[Self, np.ndarray], Tuple[Self, np.ndarray, np.ndarray]]:
+    ) -> Union[
+        Miller, Tuple[Miller, np.ndarray], Tuple[Miller, np.ndarray, np.ndarray]
+    ]:
         """Return vectors symmetrically equivalent to the vectors.
 
         Parameters
@@ -585,7 +583,7 @@ def symmetrise(
 
     def angle_with(
         self,
-        other: Self,
+        other: Miller,
         use_symmetry: bool = False,
         degrees: bool = False,
     ) -> np.ndarray:
@@ -630,7 +628,7 @@ def angle_with(
 
         return angles
 
-    def cross(self, other: Self) -> Self:
+    def cross(self, other: Miller) -> Miller:
         """Return the cross products of the vectors with the other
         vectors, which is considered the zone axes between the vectors.
 
@@ -652,7 +650,7 @@ def cross(self, other: Self) -> Self:
         m.coordinate_format = new_fmt[self.coordinate_format]
         return m
 
-    def dot(self, other: Self) -> np.ndarray:
+    def dot(self, other: Miller) -> np.ndarray:
         """Return the dot products of the vectors and the other vectors.
 
         Parameters
@@ -669,7 +667,7 @@ def dot(self, other: Self) -> np.ndarray:
         self._compatible_with(other, raise_error=True)
         return super().dot(other)
 
-    def dot_outer(self, other: Self) -> np.ndarray:
+    def dot_outer(self, other: Miller) -> np.ndarray:
         """Return the outer dot products of the vectors and the other
         vectors.
 
@@ -687,7 +685,7 @@ def dot_outer(self, other: Self) -> np.ndarray:
         self._compatible_with(other, raise_error=True)
         return super().dot_outer(other)
 
-    def flatten(self) -> Self:
+    def flatten(self) -> Miller:
         """Return the flattened vectors.
 
         Returns
@@ -699,7 +697,7 @@ def flatten(self) -> Self:
         m.coordinate_format = self.coordinate_format
         return m
 
-    def transpose(self, *axes: Optional[int]) -> Self:
+    def transpose(self, *axes: Optional[int]) -> Miller:
         """Return a new instance with the data transposed.
 
         The order may be undefined if :attr:`ndim` is originally 2. In
@@ -725,7 +723,7 @@ def get_nearest(self, *args) -> NotImplemented:
         """NotImplemented."""
         return NotImplemented
 
-    def mean(self, use_symmetry: bool = False) -> Self:
+    def mean(self, use_symmetry: bool = False) -> Miller:
         """Return the mean vector of the set of vectors.
 
         Parameters
@@ -745,7 +743,7 @@ def mean(self, use_symmetry: bool = False) -> Self:
         m.coordinate_format = self.coordinate_format
         return m
 
-    def reshape(self, *shape: Union[int, tuple]) -> Self:
+    def reshape(self, *shape: Union[int, tuple]) -> Miller:
         """Return a new instance with the vectors reshaped.
 
         Parameters
@@ -764,7 +762,7 @@ def reshape(self, *shape: Union[int, tuple]) -> Self:
 
     def unique(
         self, use_symmetry: bool = False, return_index: bool = False
-    ) -> Union[Self, Tuple[Self, np.ndarray]]:
+    ) -> Union[Miller, Tuple[Miller, np.ndarray]]:
         """Unique vectors in ``self``.
 
         Parameters
@@ -809,7 +807,7 @@ def unique(
         else:
             return m
 
-    def in_fundamental_sector(self, symmetry: Optional["Symmetry"] = None) -> Self:
+    def in_fundamental_sector(self, symmetry: Optional["Symmetry"] = None) -> Miller:
         """Project Miller indices to a symmetry's fundamental sector
         (inverse pole figure).
 
@@ -856,7 +854,7 @@ def in_fundamental_sector(self, symmetry: Optional["Symmetry"] = None) -> Self:
 
     # -------------------- Other private methods --------------------- #
 
-    def _compatible_with(self, other: Self, raise_error: bool = False) -> bool:
+    def _compatible_with(self, other: Miller, raise_error: bool = False) -> bool:
         """Whether ``self`` and ``other`` are the same (the same crystal
         lattice and symmetry) with vectors in the same space.
 
diff --git a/pyproject.toml b/pyproject.toml
index ec28e9d9..314d5025 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,8 +36,6 @@ dependencies = [
     "pycifrw",
     "scipy",
     "tqdm",
-    # TODO: Remove once Python >= 3.11
-    "typing_extensions",
 ]
 
 [project.optional-dependencies]
@@ -49,7 +47,8 @@ doc = [
     "memory_profiler",
     "nbconvert                      >= 7.16.4",
     "nbsphinx                       >= 0.7",
-    "numpydoc",
+    # Restriction due to https://github.com/pyxem/orix/issues/570
+    "numpydoc != 1.9.0",
     "pydata-sphinx-theme",
     "scikit-image",
     "scikit-learn",
@@ -100,12 +99,16 @@ addopts = [
     "-ra",
     "--ignore=doc/_static/img/colormap_banners/create_colormap_banners.py",
     "--ignore=examples/*/*.py",
+    "--strict-markers",
 ]
 doctest_optionflags = "NORMALIZE_WHITESPACE"
 filterwarnings = [
     "ignore:Deprecated call to `pkg_resources:DeprecationWarning",
     "ignore:pkg_resources is deprecated as an API:DeprecationWarning",
 ]
+markers = [
+    "slow: mark test as slow",
+]
 
 [tool.isort]
 profile = "black"