tests: integration

[pared]

We need some end-to-end tests verifying that provided renderers gets converter to expected HTML. So far we only have those for parallel coordinates plot.

[daavoo]

Duplicate #4 ?

[skshetry]

Also see: iterative/dvc#6900 (comment) for e2e tests running in the browser.

[pared]

Not quite, those two are about testing HTML, so verifying that the rendering gets done and no errors are thrown on JS side. However what I mean here is that we should prepare a tests making sure that particular data points get converted into particular HTML. They might be joined with #4 but not necessarily. Our current tests resemble unit tests more than end-to-end tests.