Tests in classic editor

[mremiszewski]

Suggested merge commit message (convention)

Tests (classic-editor): Add tests for menu bar. Related to #15894.

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Additional information

For example – encountered issues, assumptions you had to make, other affected tickets, etc.

[oleq]

This is a follow-up: We're going to need this kind of logic for the menu bar as well.

ckeditor5/packages/ckeditor5-ui/src/editorui/editorui.ts

Lines 437 to 464 in 76919d5

	editor.keystrokes.set( 'Esc', ( data, cancel ) => {
	const focusedToolbarDef = this._getCurrentFocusedToolbarDefinition();
	if ( !focusedToolbarDef ) {
	return;
	}
	// Bring focus back to where it came from before focusing the toolbar:
	// 1. If it came from outside the engine view (e.g. source editing), move it there.
	if ( lastFocusedForeignElement ) {
	lastFocusedForeignElement.focus();
	lastFocusedForeignElement = null;
	}
	// 2. There are two possibilities left:
	// 2.1. It could be that the focus went from an editable element in the view (root or nested).
	// 2.2. It could be the focus went straight to the toolbar before even focusing the editing area.
	// In either case, just focus the view editing. The focus will land where it belongs.
	else {
	editor.editing.view.focus();
	}
	// Clean up after the toolbar if there is anything to do there.
	if ( focusedToolbarDef.options.afterBlur ) {
	focusedToolbarDef.options.afterBlur();
	}
	cancel();
	} );

I coded the prototype as fast as possible so I didn't consider cases where the focus must get back to some other place (e.g. source editing).

I suppose EditorUI#addMenuBar corresponding to addToolbar would be a good idea. Because currently, the keystroke handling code for the menu bar is in ClassicEditorUI, and if sb wanted to build their editor, they wouldn't be able to add a menu bar without duplicating the code.

cc @DawidKossowski