Merge pull request #280 from ornlneutronimaging/doc_integration_test_data_setup

===================

Integration tests will typically require data from the **data repository**

located in `iMars3D/tests/data/imars3d-data/` as a

located in ``iMars3D/tests/data/imars3d-data/`` as a

`git submodule <https://git-scm.com/book/en/v2/Git-Tools-Submodules>`_.

TL;DR

-----

Perform the following steps after cloning the repo and ``cd`` to the root of the repo:

- ``sudo apt install git-lfs``  (if not already installed)

- ``git submodule init``

- ``git submodule update``

Now you should have the integration test data downloaded to ``iMars3D/tests/data/imars3d-data/``.

If you are interested in how it is configured, please continue reading.

Git Submodule

-------------

**typical commands:**

Here, "submodule" refers to repo `imars3d-data` and "parent" refers to repo `imars3d`

Here, "submodule" refers to repo ``imars3d-data`` and "parent" refers to repo ``imars3d``

- checkout the submodule after cloning the parent with command `git submodule init`

- find the refspec stored in the parent with command `git ls-tree $(git branch --show-current) tests/data/imars3d-data`

- synchronize the submodule to the refspec stored in the parent with command `git submodule update`

- after making commits in the sumodule, synchronize the refspec stored in the parent with commands `git add...` and `git commit...`

- checkout the submodule after cloning the parent with command ``git submodule init``

- find the refspec stored in the parent with command ``git ls-tree $(git branch --show-current) tests/data/imars3d-data``

- synchronize the submodule to the refspec stored in the parent with command ``git submodule update``

- after making commits in the sumodule, synchronize the refspec stored in the parent with commands ``git add...` and `git commit...``

Pytest Fixtures

===============

Pytest fixtures in `conftest.py` providing directories frequently accessed:

Pytest fixtures in ``conftest.py`` providing directories frequently accessed:

+--------------+----------------------------------------------------------------------------+

| Fixture      | Value (as a `pathlib.Path` object)                                         |

Writing Test Functions

======================

Test functions accessing `DATA_DIR` should be marked with the `datarepo` marker

Test functions accessing ``DATA_DIR`` should be marked with the ``datarepo`` marker

.. code:: python