Make tests (more) HTML ID agnostic

Input from folks with more expirience in such tests appreciated!
How does core and/or other modules do this?

Looked a bit into \Drupal\FunctionalJavascriptTests\JSWebAssert and the proposal to use XPath seems to make most sense to me.

> XPath can be pretty hard to read.

Good point. If we need them, we should at least have link name comments for maintainability.

I'd prefer the name selector (text/title/alt) too. But in our case we'll by designe have several "Title"s. Can we discriminate them? Something like $session->getXpathFragment('/path/to/second/ief')->findName('Title')?

Thought and researched a bit.

Some selenium tutorials speak about "relative selectors" beginning with "//" that "start in the middle of a document". That is plain nonsense in xpath terms, as "//" is the any-descentant syntax.

But it's quite simple to have something like getElementByNthContextAndLabelText($cssClass, $index, $label) that spits out xpath like //*[contains(concat(" ", normalize-space(@class), " "), " {$cssClass} ")][{$index}]//*[@id=string(//label[.='{$label}']/@for)]. (Note that most of the complexity stems from the fact that i chose CSS class for context and we must teach XPath to parse CSS classes.)(The XPath is tested on a form via the inspector's find-by-XPath feature.)

@Spokje, any news on this? Need any help (or just time ;-)?

@Spokje Impressing work!

Now i found some time to look into this. I like the approach of generating the xpath, this makes the magic less magic.
I'll play with the xpath to try make that more specific.

I took the xpath-fu of #10 and adapted it to label. Now we should get exactly the right element even in edge cases. Let's see if that holds.

Cool this passes too.

I went all through this patch and everything looks good to me.

More than a hundred times pain relief like this, how hot is this...🐳

+++ b/tests/src/FunctionalJavascript/ComplexWidgetTest.php
-    $page->fillField('multi[form][inline_entity_form][entities][0][form][title][0][value]', 'Duplicate!');
-    $page->fillField('multi[form][inline_entity_form][entities][0][form][first_name][0][value]', 'Bojan');
+    $title_field_xpath = $this->getXpathForNthInputByLabelText('Title', 2);
+    $first_name_field_xpath = $this->getXpathForNthInputByLabelText('First name', 1);
+    $assert_session->elementExists('xpath', $title_field_xpath)->setValue('Duplicate!');
+    $assert_session->elementExists('xpath', $first_name_field_xpath)->setValue('Bojan');
     $create_node_button->press();

> And _then_ we can finally tackle this issue, which was what I came in for, many, many moons ago

Aah, i remember dimly... Hey, passing the marshmallow test is said to be a predictor for a good life. ;-)

I committeed the other issue, thanks for that! And here's a re-roll.

So finally that's in. Champagne! And marshmallows. 🍾🥂