The work on the streams tests is closely tracked by the specification authors, who maintain a reference implementation intended to match the spec line-by-line while passing all of these tests. See the whatwg/streams repository for details. Some tests may be in that repository while the spec sections they test are still undergoing heavy churn.
Because the streams feature is supposed to work in all global contexts, each test is written as a .js file, and then four .html files are generated around it. So for example, for count-queueing-strategy.js, we have the wrapper files:
count-queueing-strategy.https.htmlcount-queueing-strategy.dedicatedworker.htmlcount-queueing-strategy-sharedworker.htmlcount-queueing-strategy-serviceworker.htmlThese are generated automatically by the Node.js script in generate-test-wrappers.js. See it for details, and please remember to use it whenever adding new tests.