Tests: fix Stream assertions

This doesn't change any expectations, only uses the much more useful overloads like Assert.Equal(a, b) instead of Assert.True(a == b) so we get much more useful output.

Something is wrong with our stream assumptions, but it's not super clear on what special IDs are what in the docuemtnation right now either...I think our resolution to special start IDs is off but let's get testing in order first.