Convert AJAX part of \Drupal\ckeditor\Tests\CKEditorAdminTest::testExistingFormat to JavascriptTestBase

I made an attempt at converting this test. There are several problems still though.

- There are JavaScript problems after adding a group, I have actually reproduced these but can't exactly figure out how. If I know how I should either upgrade this issue to a bug or open a new issue?
- Divider dragging doesn't work yet.
- Enabling the ckeditor_test module causes all kinds of problems somehow.
- Test still failes.

Posting my work in progress, curious if anyone has suggestions on fixing it.

I figured out some more on the JavaScript error.

The error is: Error: cannot call methods on dialog prior to initialization; attempted to call method 'option'

It's triggerd in dialog-position.js on line 62, a handler for a window resize event for the dialog. In the test (and on very rare occasions) it's triggered when the event handler is still triggered while the dialog is not there anymore.

I fine-tuned the patch a little and with the module testing disabled and the lines in dialog-position.js disabled the test now passes.

I also used a simplyfied Styles input as there are problems with the endline in the test.

Todo:
- Figure out why the module cannot be enabled while it could in the old test
-- I think it has something to do with the fact that JavaScript is actually executed and now causes problems, making the ckeditor_test module unusable in it's current state.
- Figure out a way to fix the dialog JavaScript error
- Maybe find out why the Styles input can't handle a newline?
-- Manually comparing the results (fileMerge) states the strings are identical, the assertion disagrees. It must be an invisible character difference.

1. +++ b/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php
   @@ -73,47 +73,17 @@ function testExistingFormat() {
        );
   +
        $this->drupalPostForm(NULL, $edit, t('Save configuration'));
   ...
   +    return;
   +
   
   @@ -157,38 +127,6 @@ function testExistingFormat() {
   diff --git a/core/modules/ckeditor/tests/modules/css/llama.css b/core/modules/ckeditor/tests/modules/css/llama.css
   
   diff --git a/core/modules/ckeditor/tests/modules/css/llama.css b/core/modules/ckeditor/tests/modules/css/llama.css
   new file mode 100644
   
   new file mode 100644
   index 0000000..e69de29
   
   index 0000000..e69de29
   diff --git a/core/modules/ckeditor/tests/modules/js/llama.js b/core/modules/ckeditor/tests/modules/js/llama.js
   
   diff --git a/core/modules/ckeditor/tests/modules/js/llama.js b/core/modules/ckeditor/tests/modules/js/llama.js
   new file mode 100644
   
   new file mode 100644
   index 0000000..e69de29
   
   index 0000000..e69de29
   diff --git a/core/modules/ckeditor/tests/modules/js/llama_button.js b/core/modules/ckeditor/tests/modules/js/llama_button.js
   
   diff --git a/core/modules/ckeditor/tests/modules/js/llama_button.js b/core/modules/ckeditor/tests/modules/js/llama_button.js
   new file mode 100644
   
   new file mode 100644
   index 0000000..e69de29
   
   index 0000000..e69de29
   diff --git a/core/modules/ckeditor/tests/modules/js/llama_contextual.js b/core/modules/ckeditor/tests/modules/js/llama_contextual.js
   
   diff --git a/core/modules/ckeditor/tests/modules/js/llama_contextual.js b/core/modules/ckeditor/tests/modules/js/llama_contextual.js
   new file mode 100644
   
   new file mode 100644
   index 0000000..e69de29
   
   index 0000000..e69de29
   diff --git a/core/modules/ckeditor/tests/modules/js/llama_contextual_and_button.js b/core/modules/ckeditor/tests/modules/js/llama_contextual_and_button.js
   
   diff --git a/core/modules/ckeditor/tests/modules/js/llama_contextual_and_button.js b/core/modules/ckeditor/tests/modules/js/llama_contextual_and_button.js
   new file mode 100644
   
   new file mode 100644
   index 0000000..e69de29
   
   index 0000000..e69de29
   diff --git a/core/modules/ckeditor/tests/modules/js/llama_css.js b/core/modules/ckeditor/tests/modules/js/llama_css.js
   
   diff --git a/core/modules/ckeditor/tests/modules/js/llama_css.js b/core/modules/ckeditor/tests/modules/js/llama_css.js
   new file mode 100644
   
   new file mode 100644
   index 0000000..e69de29
   

   Unrelated changes. Should be reverted.

2. +++ b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorAdminTest.php
   @@ -0,0 +1,221 @@
   +  /**
   +   * Modules to enable.
   +   *
   +   * @var array
   +   */
   

   {@inheritdoc}

3. +++ b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorAdminTest.php
   @@ -0,0 +1,221 @@
   +  public static $modules = array('filter', 'editor', 'ckeditor');
   

   I think is protected in 8.3.x and let's use the square brackets syntax for arrays.

Very sorry about this, I forgot to upload my files and you reviewed a slightly older patch. I already removed the extra js files.

I fixed the other 2 issues with comments and code formatting.

My earlier todolist is still valid though..

I updated the summery with the remaining tasks. I also found out more about why the module doesn't work and did work, there are JavaScript errors because the llama plugin is not defined correctly.

Added reproducable steps and cause for the JavaScript error in the dialog. Really seems that it's actually a bug, it's harmless in the actual UI but it will make the test fail.

I moved the test for enabling the module back to the original test as it wasn't actually testing anything javascripty.

I updated the Functional test to fix some minor problems, I think it's good for a proper review now.

While searching the issues I found an existing issue for the dialog problem: #2731419: "cannot call methods on dialog prior to initialization" logged when resizing after closing a modal. This issue will need to be committed before this test will pass.

edit: waiting for needs review untill the related issue is fixed.

Small update to use the new wait...() methods. Let's see if it passes now that mentioned issue is fixed.

This actually got 'fixed' by #2863996: Convert web tests to browser tests for ckeditor module.