Add some automated tests

Automated testing is quite new to me but I'm starting to love it. It's a struggle though to set it up in the first place. I actually wrote 2 functional tests yesterday and thought I'd use the same environment and voila Error: Class 'org\bovigo\vfs\vfsStream' not found :D
composer require mikey179/vfsstream --dev fixes that but there's something else going on. I think you're running them somehow differently because I'm getting the same errors as is the results of #5.

Basically what I run is this:
./vendor/bin/phpunit web/modules/contrib/high_contrast/tests/src/FunctionalJavascript/HighContrastStyleSheetTest.php
or

./vendor/bin/phpunit web/modules/contrib/high_contrast/

You should have 7.5 if you're running on Drupal 8.8:

./vendor/bin/phpunit --version
PHPUnit 7.5.20 by Sebastian Bergmann and contributors.

But to the tests

1.
Drupal\Tests\high_contrast\FunctionalJavascript\HighContrastStyleSheetTest::testStyleSheetGenerated
Error: Call to undefined function file_save_data()

This one was strange. You can basically disable everything in the test and you still got the error. Seems though what is triggering it adding 'high_contrast' to $modules :S

In the mean time I had to also install selenium

lando composer require behat/mink-selenium2-driver --dev

Ok, so file_save_data() is used in high_contrast_install() and that breaks it. So file is not test dependency, but module dependency.

dependencies:
  - drupal:file

What's odd for me is that I can't remove the file dependendy from test. Maybe it's KernelTestBase peculiarity

I also added - drupal:block as dependency as I know the module adds block.

2.
I see this patch will conflict with https://www.drupal.org/project/high_contrast/issues/3114528 There I did changes like:

-  function enable_high_contrast() {
+  public function enableHighContrast() {

Could we merge that and then do updates here?

3.
Drupal\Tests\high_contrast\Kernel\HighContrastConfigOverrideTest::testConfigurationOverrides
Drupal\Component\Plugin\Exception\PluginNotFoundException: The "user" entity type does not exist.

In this case it seems that $this->installEntitySchema() needs user. I searched in core and there are about 5 tests where it's used and all have user as dependency. The error is gone.

4.
New errors now, yay! :D

Drupal\Tests\high_contrast\FunctionalJavascript\HighContrastStyleSheetTest::testStyleSheetGenerated
Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException: Circular reference detected for service "theme_handler", path: "theme_handler -> config.factory -> high_contrast.overrider -> theme.manager -> theme.negotiator -> access_check.theme".

Ok, so I searched for "{ name: config.factory.override }" in core and none of them had any arguments, which was suspicious. Then I came across https://www.drupal.org/docs/8/api/configuration-api/configuration-overri... . One sentence there cought my eye:

It is worth reiterating that if you need to read the original configuration values in an override, for example, to compare or merge, you would need to load from the \Drupal::configFactory and not \Drupal::config to avoid a nested loop into your override: -
$original = \Drupal::configFactory()->getEditable('system.site')->getOriginal('name', FALSE);

But as the error is about theme, I removed '@theme.manager' from arguments and instead used \Drupal::theme(). No more errors

But now I'm at point where it says

OK, but incomplete, skipped, or risky tests!
Tests: 2, Assertions: 2, Skipped: 2.

1.2
Tx about info on kernel tests!

1.3
About the block dependency. I think it should be there until the module can be used theoretically without block :) Main way how to enable/disable Drupal 7 High Contrast is to use tab key. Maybe now it also has block in D7, but that was the original idea. It's used here for example https://www.valitsus.ee/en - press tab 3 times and you'll see 'Toggle high contrast' link, then press enter. So if that feature would be in Drupal 8, then I would treat block as soft dependency. I propose new task for this feature. What do you think?

2. Cool, tx! I'll re-add the patch against latest changes.

4. Still have to wrap around my head on this change. Haven't had time but will get back to this tomorrow.

Adding patch against latest changes in repo. Interdiff is a bit confusing. Maybe I was too tired but should be ok. There is not trace of enable_high_contrast left in the new patch.

-  public function enable_high_contrast() {
+  function enable_high_contrast() {

Nice, tx!