Add rendering tests for the demos and add images to README

[xhluca]

About

Description of changes

Pre-Merge checklist

• The project was correctly built with npm run build.
• If there was any conflict, it was solved correctly.
• All changes were documented in CHANGELOG.md.
• All tests on CircleCI have passed.
• All Percy visual changes have been approved.
• Two people have 💃'd the pull request. You can be one of these people if you are a Dash core contributor.

Reference Issues

Closes #[issue number]

Other comments

[xhluca]

@jourdain the tests are failing. Can you see them?

[xhluca]

―――――――――――――――――――――――――――― test_usage_vtk_cfd.app ――――――――――――――――――――――――――――

dash_duo = <dash.testing.composite.DashComposite object at 0x7f9de5bbb320>

    def test_fn(dash_duo):
>       app = import_app(name)

tests/test_render.py:33: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
venv/lib/python3.6/site-packages/dash/testing/application_runners.py:43: in import_app
    app_module = runpy.run_module(app_file)
/usr/local/lib/python3.6/runpy.py:208: in run_module
    return _run_code(code, {}, init_globals, run_name, mod_spec)
/usr/local/lib/python3.6/runpy.py:85: in _run_code
    exec(code, run_globals)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

    import dash
    import dash_vtk
    import dash_bootstrap_components as dbc
    import dash_html_components as html
    import dash_core_components as dcc
    from dash.dependencies import Input, Output, State
    
    import vtk
    import pyvista as pv
    import numpy as np
    from vtk.util.numpy_support import vtk_to_numpy
    
    import os
    import random
    
>   from color_maps import presets
E   ModuleNotFoundError: No module named 'color_maps'

demos/usage-vtk-cfd/app.py:16: ModuleNotFoundError

 tests/test_render.py::test_usage_vtk_cfd.app ⨯                   86% ████████▋ 
 tests/test_render.py::test_usage_algorithm.app ✓                100% ██████████
=============================== warnings summary ===============================
tests/test_render.py: 26 warnings
  /home/circleci/project/venv/lib/python3.6/site-packages/urllib3/util/retry.py:255: DeprecationWarning:
  
  Using 'method_whitelist' with Retry is deprecated and will be removed in v2.0. Use 'allowed_methods' instead

-- Docs: https://docs.pytest.org/en/stable/warnings.html

Results (69.51s):
       4 passed
       3 failed
         - tests/test_render.py:32 test_usage_pyvista_terrain_following_mesh.app
         - tests/test_render.py:32 test_usage_pyvista_point_cloud.app
         - tests/test_render.py:32 test_usage_vtk_cfd.app

Exited with code exit status 1
CircleCI received exit code 1

[xhluca]

Did you add vtk and color_maps into the demos/app-name/requirements.txt? I can't seem to find color_maps on pypi

[jourdain]

I did for vtk, color_maps is local to the directory.

[jourdain]

I'll move colormap to the utils at some point... Working the quarks now...

[xhluca]

No worries. Feel free to push to this branch and merge this when you are done!

[jourdain]

Several fix went to master. The preset/colormaps is now part of dash_vtk.util. I've fixed the import in the demos...

[jourdain]

Don't forget to re-run npm i

[xhluca]

Seems like there's an error with test_usage_pyvista_point_cloud

[xhluca]

Ok looks like the problems went away.

@jourdain I'm gonna merge this but I just wanted to make sure you are able to view the percy changes before merging; let me know!

[jourdain]

LGTM, what is you are able to view the percy changes?

[xhluca]

@jourdain if you click on the "percy/dash-vtk - 5 visual changes need review" can you see the changes?

[jourdain]

Where do I find percy/dash-vtk - 5 visual changes need review?

[xhluca]

Ok I just enabled it (was a bit counter-intuitive) you should be able to see it now along with the circleci tests!

[xhluca]

[jourdain]

I see the screenshots and they are fine. Do I need to do something?

[xhluca]

No, just wanted to make sure it works! Gonna merge now