Streaming/SSE Scenario tests

[lmazuel]

Add Spector tests for everything streaming

[lmazuel]

we added two tests a long time ago. Since Chenjie wrote them, not sure they are enough
#6201

We added them with the initial goal to check that using streaming do not crash the emitter, and can successful return the whole stream as bytes (less good experience, but still better than nothing). So the mindset was not into completeness of the feature.