Use com.vaadin.flow.uitest.ui.StreamResourceView test.

It sets a link (a element) with a dynamic resource via StreamResource:

 StreamResource resource = new StreamResource("filename",
                () -> new ByteArrayInputStream(
                        "foo".getBytes(StandardCharsets.UTF_8)));
        Anchor download = new Anchor("", "Download file");
        download.setHref(resource);
        download.setId("link");
        add(download);

Open the http://localhost:8888/view/com.vaadin.flow.uitest.ui.StreamResourceView page.
There will be a link.
Click on it.

Result: there is an attempt to apply a routing for the URI. But there is no such route. Navigation can't be done and there is a routing error.

Expected: the file is downloaded.

In fact the file can be downloaded : you may copy a link to the clipboard and open it in another tab.
Then everything works fine.

So apparently routing is applied when it should not be applied. That worked fine without CCDM.
Most likely broken because of CCDM.