Matching against text content of the multi-line HTML pieces is tricky

[manicki]

This has been discovered in https://gerrit.wikimedia.org/r/#/c/348756/2/resources/templates.php.
There HTML being validated is generated from the template. For convenience it makes sense to have a bit complex HTML split into multiple lines.

Resulting HTML could then be something like:

<div>
    <span class="foo">This is just an example.</span>
    <span class="quux">More text:
        <span class="value">Foo</span>
    </span>
</div>

If for any reason it was important to check this HTML piece contains "More text: Foo", current implementation of havingTextContents (ie. havingTextContents(constainsString('More text: Foo')) would fail to do so. This is because currently it strictly checks the text contains expected substring including all the whitespace.

In order to deal with cases like the above, there could be a custom matcher added ignoring the whitespace.
The alternative way might be to change havingTextContents do the whitespace normalization magic. I don't think this would be nice, though. On the other hand, that would kind of be replicating the behaviour of browsers etc, that also treat multiple white space as a single one.