Add tests for ImageGrid

[oscargus]

PR Summary

Add tests for ImageGrid.

Minor correction to docs and code as one can get the impression that a string can be passed as rect, but this will give an error later on.

PR Checklist

Tests and Styling

• Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs should build without error).

[QuLogic]

Oh, also, do you need text; can you set remove_text=True?

[timhoffm]

I suggest to connect the colorbars with the respective axes images, so that they are not empty. C.f. https://matplotlib.org/stable/gallery/axes_grid1/demo_axes_grid.html

Also, not sure if it’s worth it here, but I generally try to introduce asymmetry into tests, e.g. (2,3) instead of (2,2) so that the test gets sensitive to a mixup of rows/columns.

[oscargus]

Oh, also, do you need text; can you set remove_text=True?

I also test label_mode, so the text is required to see the effect.

[oscargus]

I suggest to connect the colorbars with the respective axes images, so that they are not empty. C.f. https://matplotlib.org/stable/gallery/axes_grid1/demo_axes_grid.html

Also, not sure if it’s worth it here, but I generally try to introduce asymmetry into tests, e.g. (2,3) instead of (2,2) so that the test gets sensitive to a mixup of rows/columns.

Sure, I can modify the tests like that.

[oscargus]

This is updated based on the comments, including expanding the test names to tell what is tested.

It is maybe not a good idea to test two features, colorbar and label_mode in the same test, but there will be quite a lot of images testing all combinations...

[timhoffm]

This is updated based on the comments, including expanding the test names to tell what is tested.

It is maybe not a good idea to test two features, colorbar and label_mode in the same test, but there will be quite a lot of images testing all combinations...

As far as I understand, label_mode and colorbar do not depend on each other, so explicit combinations of these need not be tested.

label_mode can easily be tested algorithmically by checking visibility attributes. I don't think we need images for that. This has the added benefit that these tests become independent of the visual representation of ticks and labels.

[oscargus]

I was a bit unclear. I was referring to combination of colorbar combinations ('each', 'single', 'edge') x ('left', 'right', 'top', 'bottom').

Not so clear why the colorbar content should be in the test (which is not at all related to ImageGrid as such), but the text should not (which allows visible inspection of what should happen).