## Summary
Many tests proved a specific change when it landed but don't need to run on every CI build forever. This removes **202 test methods and 9 files: 313 test cases, 2,247 → 1,934**. UOContent.Tests drops from about 14s to about 5s locally.
Removed:
- **Tautologies.** Asserting a constant, a constructor readback or a trivial getter, or testing BCL behavior.
- **Exact duplicates** of a surviving test on the same code path.
- **Obsolete regressions** whose failure can no longer be expressed.
- **Game-content values** shard owners customize (era drop rates, loot and skill tables, single-creature tuning). Each customization would otherwise force a test fix.
## How it was decided
1. Every test was classified, with a reason, by a per-shard sweep over all 287 test files.
2. Each proposed deletion was then checked by a second, adversarial reviewer against the surviving tests and the production code.
3. Anything that was the only coverage of a separate code path was **kept**, even where it looked like a duplicate. Examples: the unsigned `SpanReader`/`SpanWriter` methods, the at-location versus bounds enumerators, null-map enumerables, the security filters, archive-journal state transitions. About 130 proposed deletions were rejected this way.
Whole files removed:
- `FishingTests`, apart from 3 tests: the map-edge scan, serpent cleanup, and SOS chest consumption. The SOS test now stops at the first chest instead of measuring a catch rate. The multi-million-cast rate simulations are gone.
- `LordOaksTests` and `MeerEnragedTests` (single-creature tests).
- `AutoArchiveHelperTests`, `JsonDiscoverableTypeAttributeTests`, `DecimalSerializationTests` and `EnumConversionTests` (tautologies, or tests of their own local helpers).
- `NetworkStatsTests`.
- `MigratedDataLoadTests` (a subset of `AllSpawnFilesLoadTests`).
- `SpawnerFixtureCapture`: a capture tool, not a test, and its `version == 12` assert can no longer pass. The `.bin` fixtures it produced stay.
## Tests
- Server.Tests: 811 pass.
- UOContent.Tests: 1,123 pass.
A follow-up PR, stacked on this one, fixes how the remaining tests behave: shared state, CI-vacuous tests, harness duplication.
## Summary
Two related fixes on the outbound path:
1. Consume **IORingGroup 1.0.8**, which allows more than one send in flight per socket, and expose the two settings that go with it.
2. Stop `NetState.Send` silently discarding packets when the send buffer fills — including an out-of-bounds write reachable in that state.
## 1. Send-path stall (RIO)
RIO reports send completion on **acknowledgement**, not on copy, so a completion cannot arrive sooner than one round trip. With one send in flight, `PostSend` refused to post again until the previous completion arrived — capping a connection at **one send per RTT** whenever it had data queued.
Measured on a 50ms-RTT production shard:
| | before | after |
|---|---|---|
| in-game latency, data flowing | **101–146 ms** | **48–51 ms** |
| p95 | ~135 ms | 52.8 ms |
| samples > 70 ms | 20 | **0** |
The control that confirms the mechanism: server-side post→completion was **unchanged** at median 92ms across both runs. The ACK-binding is inherent to RIO and did not move; only its propagation into application latency did.
Two things worth recording, because they explain why this went unnoticed:
- As little as **6 bytes** of queued data held the gate shut, so it reproduced in empty areas, not just crowded ones.
- The same measurement at loopback RTT is **microseconds**, so local testing could never surface it.
New settings, both restart-time:
- **`network.maxOutstandingSends`** (default 32) — sends in flight per connection. Honoured by RIO only; other backends complete sends on copy and report 1. Costs a request-queue and completion-queue slot per send, **not another buffer**, since every outstanding send addresses a different range of the same registered buffer. Worst-case added latency is roughly `completion RTT / value`.
- **`network.sendBufferSize`** (default 256KB) — per-connection send buffer, coerced to a power of two of at least the platform allocation granularity. This is the lever for the disconnects below, and the per-connection memory ceiling.
## 2. Send buffer full
`NetState.Send` had three failure modes once the buffer filled, none of them visible:
| writable | behaviour |
|---|---|
| `0` | `GetSendBuffer` returned false → **packet dropped**, no log, no disconnect |
| `4 … needed-1` | `Compress` returned 0 → `CommitWrite(0)` → **packet dropped** the same way |
| `1 … 3` | `safeOutputLength = (nuint)output.Length - 4` **underflows** → hot-loop bounds check never trips → **writes past the span** |
The first two leave a client connected while quietly missing game state, which is undiagnosable from either end. The third corrupts the in-flight region of the ring buffer, and is reachable precisely when a connection is congested, since callers only check for non-zero space.
`Compress` now refuses an output too small to bound, and `Send` reports exhaustion instead of dropping — logging and disconnecting with **needed / writable / unacked / capacity**. Those numbers separate a slow client holding the buffer from a buffer genuinely too small for the shard, which is the case that warrants raising `network.sendBufferSize`.
## Testing
`NetworkCompressionBoundsTests` covers the underflow using sentinel bytes around the output window. **Verified to fail without the guard** (4 failures from overwritten sentinels), confirming the out-of-bounds writes were real rather than theoretical.
Full suites green: **788 Server.Tests**, **597 UOContent.Tests**, Release build clean against the published 1.0.8.
## Notes for reviewers
- Upstream change: modernuo/IORingGroup#9.
- The buffer-full path is now *loud* where it used to be silent. If a shard has been quietly dropping packets under load, this will surface as disconnects — that is the intended outcome, and the log line says which setting to raise.
- Follow-up under discussion: promoting a connection to a larger buffer instead of disconnecting, which looks feasible on a live connection since buffers are referenced per-operation rather than bound to the request queue.
Kamron Batman