ConfigImporterException: There were errors validating the config synchronization.

Ummm, it seems that something is mixing code from tests with code outside tests. Let me have a look into it and I'll try to fix it ASAP.

Thanks for you help!

I have published a new released (8.x-1.16) that fixes this issue.

Thanks for your patch @facine, but, for unknown reasons, hook_preprocess_html()is not executed on tests unless your theme is called the same as your module, so just changing the test theme to "critical_css_theme_test" or similar will fix the problem on normal execution, but will make tests fail. I have had to refactor some parts of the module to get rid of that hook_preprocess_html() hook, and move all its code to another part of the module.

Please let me know if this new version fixes the problem, I will wait for your confirmation before closing the issue.

Thank you very much.

@facine, any update on this?

Will close this issue since no response given.

Please, don't hesitate to reopen it if something doesn't work.