## Summary
About 114 tests skipped on CI because they needed the official client files (`tiledata.mul`, map and multi files). They gave CI no signal, and locally they ran against whichever client a developer had installed. The test hosts now build their own world instead, so every test runs on CI and runs the same on every machine. CI simulation: Server.Tests 837 passed, UOContent.Tests 1131 passed, **0 skipped**.
- **Generated tile data.** The fixtures write a pre-HS `tiledata.mul` from a small invented tile kit (`Server.Tests/Terrain/TestTiles`) and load it through the real `TileData.Load()`. The test hosts no longer read any client directory (`MODERNUO_CLIENT_PATH`, `MODERNUO_TEST_DATA_DIR` and `C:\Ultima Online Classic` are gone from test code). The file is written to `SyntheticData` in each test project's output, overwritten every run and removed by `dotnet clean`.
- **Injected terrain.** `TestTerrain` stamps land and statics into Felucca and Trammel, which share one terrain. Writes after startup must go in a `TestTerrain.Scope()`, which puts back every block it touched and keeps the step cache fresh.
- **Prefab scenes.** Seven named scenes (town, causeway, sewer walkway, coastline, deep sea, map-edge sea, an upstairs room with an L-shaped counter) replace the Britain coordinates the pathing, AI and fishing tests relied on. Each scene-based test asserts its scene is present first, so a missing scene fails instead of passing on flat ground. Stamping all seven takes 3-5 ms.
- **Multi footprints.** Contrived footprints for the three multi IDs content looks up (0x74, 0x7A, 0x0) are seeded through a new internal `MultiData.SetComponents`.
- **Fingerprint.** `StepCacheFile.HashTileDataFile` is extracted so a test can show that a one-flag change to the file changes the fingerprint, while runtime table mutation does not.
### Engine changes
- `TileMatrix.GetLandBlock`/`GetStaticBlock`: on a map without its files, return the block injected with `SetLandBlock`/`SetStaticBlock`, or the default when nothing was injected. Maps with files take the same path as before.
- `MultiData.SetComponents` (internal): registers a footprint without multi files.
### Test changes worth a look
- Values that were properties of real Britain terrain (probes at Z 10, a pinned plain walk mask of 0xC1) are re-pinned to the synthetic plain (Z 0, 0xFF).
- No tests were deleted. The multi walkability and boat-deck tests assert movement behaviour over a footprint, not what a real multi looks like, so they run on the contrived footprints.
- Maps 0 and 1 keep file indexes 0 and 1, and every stamp writes both, rather than sharing one file index. On a map without files the getters never consult the shared-file cache, and its patch bits would hide one facet's injection from the other.
## Test plan
- [x] `dotnet test -p:SolutionDir=... --filter "Category!=Manual"` with the client env vars pointed at an empty directory: 837 + 1131 passed, 0 skipped, 0 failed
- [x] Mutation check: removing the step-cache clear from `TestTerrain` makes the stale-cache tests fail
- [x] CI green on all platforms
## Summary
Digging up a decoded treasure map of level 0, or of level 2 and above, throws inside `DigTimer.OnTick` once the chest surfaces. The exception escapes the timer, so the server goes down:
```
System.NullReferenceException: Object reference not set to an instance of an object.
at Server.Items.TreasureMap.DigTimer.OnTick() in ...\Items\Maps\TreasureMap.cs:line 809
```
#2568 made `TreasureMapChest._guardians` lazily created: the constructor no longer initialises it, and migration nulls an empty list. #2569 updated the read in `CheckLocked` to match, but the dig timer still adds each spawned guardian directly:
```csharp
if (bc != null)
{
m_Chest.Guardians.Add(bc); // null on a freshly dug chest
}
```
Level 1 maps survive only because they spawn no guardians. I confirmed the regression by running the dig test below at #2568's parent, where it passes, and at #2568, where it fails.
The dig timer now calls the generated `AddToGuardians`, which creates the list on first use.
## Testing
- `dotnet build`: 0 warnings, 0 errors.
- New `TreasureMapChestGuardianTests`:
- `Dig_AddsSpawnedGuardiansToTheChest` (levels 0 and 2) drives the real `DigTimer` tick by tick until the chest surfaces. Before the fix both cases fail with the `NullReferenceException` above. It needs client map data, so it calls `TileDataRequirement.SkipIfMissing()` and skips on CI.
- `AddToGuardians_OnNewChest_KeepsLevelZeroChestShut` needs no client data, so it runs on CI: the list starts null, the first guardian creates it, and a level 0 chest stays shut to players until that guardian is dead.
- Full `UOContent.Tests`: 1196 passed and 2 skipped with client data; 1105 passed and 93 skipped without.
