test(services): a port test that asks about MixEngine and not about the runner (T34c) - #26
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…he runner (T34c) `test (windows-latest)` went red on master at 8b9a394: `fakeservice@second` was given 41000 and `@main` a number above it, so `second == first + 1` failed. The allocator was right. It searches from the recipe's wish every time, so a machine holding 41000 while `@main` was created and releasing it before `@second` leaves exactly that pair — and **nothing in this workspace binds 41000**, which the recipe says of itself, so what held it was the runner. The test was asserting a property of the machine. What survives a busy machine, and is asserted instead: the three instances get three different ports, all inside the band `[41000, 41000 + SEARCH]`, and the one that could not have the number it wanted is told the number it wanted rather than the number it got. Measured rather than argued: with a listener held on 41000 for the whole run, the rewritten test passes and the old one could not have — it expects `moved_from.preferred` to equal a port that moved. The exact-successor claim is not dropped, it moves to where a band belongs to somebody: `a_moved_service_is_given_the_very_next_port` takes two consecutive free ports out of the 24000 window `a_free_run` now hands out, holds the first and asserts the allocation is the second. `a_free_port` is that call with a run of one. `mixengine-daemon`'s packages suite carried the same premise one assertion along — "the fixture recipe's preferred port, free in a home of its own" — and free in a home of its own was never the question. It asks for a port now.
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test (windows-latest)went red on master at 8b9a394.fakeservice@secondwasgiven 41000 and
@maina number above it, sosecond == first + 1failed.The allocator was right. It searches from the recipe's wish every time, so a
machine holding 41000 while
@mainwas created and releasing it before@secondleaves exactly that pair. And nothing in this workspace binds41000 — the fixture recipe says so of itself, and every other bind in the
tree asks for port 0 — so what held it was the runner. The test was asserting a
property of the machine.
What is asserted instead
At the end-to-end layer, only what survives a busy machine:
[41000, 41000 + SEARCH]wanted, not the number it got — the old assertion compared it against a
port that may itself have moved, so it was wrong the same way
The exact-successor claim moves rather than disappears
a_moved_service_is_given_the_very_next_portinmixengine_core::services::portstakes two consecutive free ports out of the24000 band through a new
a_free_run, holds the first and asserts theallocation is the second.
a_free_portis that call with a run of one. A bandsomebody controls is the only place the letter of the rule can be held to.
mixengine-daemon's packages suite carried the same premise one assertionalong — "the fixture recipe's preferred port, free in a home of its own" —
and free in a home of its own was never the question. It asks for a port now.
Measured
With a listener held on 41000 for the whole run, the rewritten test passes; the
old one could not have. CI green on all ten jobs.