Re: [streams] More tests to the suite (#391)

Thanks very much! Merged as c258c5750649d5ac020b44d8e4256030a458fb61, 007ff3a0171cbecf8b295abb703ea0ea09214a7b, and 0e56ed49dc66fd1b29cd08acaafad24a7c06f058, with a couple changes to make them more templated so they can apply to e.g. testing Fetch.

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