Adding test_plotting in tests

[FloraSauerbronn]

Creating test_plotting.py with the first test of plot_transect, using pytest-mpl.

[ocefpaf]

We need 3 extra steps to activate the image comparison tests here:

1. add pytest-mpl to the requirements-dev.txt file..
2. generate the comparison images with pytest --mpl-generate-path=tests/baseline.
3. add the --mpl option in the line that run the tests in .github/workflows/tests.yml.

You can find more about pytest-mpl here.

[ocefpaf]

We need to give the test function a directory where to look for the images for the comparison.

Suggested change

	@pytest.mark.mpl_image_compare
	@pytest.mark.mpl_image_compare(baseline_dir=root.joinpath("baseline/"))

[ocefpaf]

When using figures in tests we do not want matplotlib to fire up its Graphical User Interface (GUI) to avoid holding up the tests with a Window waiting to be closed.

Suggested change

	import matplotlib as mpl
	mpl.use("Agg")

[ocefpaf]

We use this to get the current directory to build the path to the baseline directory, where the images for the comparisons are held.

Suggested change

	from pathlib import Path
	root = Path(__file__).parent

[ocefpaf]

@FloraSauerbronn, as you can see the PR is failing as expected when we change the plot and the image deviates from the baseline. We can revert it back to temperature now and things should pass.

[FloraSauerbronn]

@FloraSauerbronn, as you can see the PR is failing as expected when we change the plot and the image deviates from the baseline. We can revert it back to temperature now and things should pass.

Sorry @ocefpaf, I forgot to change it back before the push

[ocefpaf]

The tests are failing now b/c there is enough difference to trigger a real mismatch. The diff image is:

That is probably b/c of fonts differences between you installation of matplotlib and the one in the CIs. BTW, what version of matplotlib do you have?

I'll regenerate the image here and push to confirm if that is the case.

[ocefpaf]

As I suspected, the matplolib on my machine was able to create an image that had a match with the one in the CIs. We could also get this to pass by adjust the tolerance but, in this case, we could solve it without resorting to that.

[ocefpaf]

pre-commit.ci autofix

[FloraSauerbronn]

The tests are failing now b/c there is enough difference to trigger a real mismatch. The diff image is:

That is probably b/c of fonts differences between you installation of matplotlib and the one in the CIs. BTW, what version of matplotlib do you have?

I'll regenerate the image here and push to confirm if that is the case.

I'm using
matplotlib 3.9.0
matplotlib-inline 0.1.7

What is the CIs ?

[ocefpaf]

What is the CIs ?

Continuous Integration. The system we are using to run the tests here.

[ocefpaf]

I'll merge this to reduce the merge conflicts and we can address the last pre-commit-ci failure in a new PR.