DST test for Engine. (#5424)

# Description of Changes

Sets the layout for DST tests and adds a basic test for
`spacetimedb-engine` via `engine` mod.

### Engine Test:
- Generates random schemas with tables, indexes, unique constraints,
primary keys, and sequence columns.
- Drives randomized interactions: begin mutable tx, insert, delete,
commit, and replay.
- Uses an in-memory commitlog/durability implementation so replay can
simulate shutdown/reopen without
    disk.
   - Define properties, check them while processing interactions.


### Upnext:
1. Fault-injection in commitlog.
2. Multi connection support (async api call-ing is not needed for
`engine` test as we expect caller/module to also be single-threaded).
3. Increase API coverage of engine, especially schema migrations.
4. Add more properties like check for sequences.
5. simulated Snapshots.

Further more integration tests like `standalone`, `replication` can be
added by implementing
[`traits.rs`](https://github.com/clockworklabs/SpacetimeDB/pull/5424/changes#diff-c9a6dc71550c7ccdd23b18de8ec8777aa6e2a34af2ddad0a5040537c8dffd1e6)
similar to `engine`.

looking to get general feedback on overall design for test effectiveness
and maintainability.




# API and ABI breaking changes
NA

# Expected complexity level and risk
It's a test addition.

Author: Shubham8287

.github/workflows/ci.yml

@@ -338,9 +338,6 @@ jobs:
 
           wasm-bindgen --version
 
-      - name: Check engine simulation build
-        run: cargo check -p spacetimedb-engine --no-default-features --features simulation
-
         # Source emsdk environment to make emcc (Emscripten compiler) available in PATH.
       - name: Run tests
         run: |

Cargo.lock

@@ -77,7 +77,7 @@ members = [
   "crates/bindings-typescript/test-app/server",
   "crates/bindings-typescript/test-react-router-app/server",
   "crates/bindings-typescript/test-solid-router/server",
-  "crates/query-builder",
+  "crates/query-builder", "crates/dst",
 ]
 default-members = ["crates/cli", "crates/standalone", "crates/update"]
 # cargo feature graph resolver. v3 is default in edition2024 but workspace

Cargo.toml

@@ -10,14 +10,14 @@ rust-version.workspace = true
 spacetimedb-data-structures.workspace = true
 spacetimedb-lib = { workspace = true, features = ["serde", "metrics_impls"] }
 spacetimedb-commitlog.workspace = true
-spacetimedb-durability = { path = "../durability", default-features = false }
+spacetimedb-durability.workspace = true
 spacetimedb-metrics.workspace = true
 spacetimedb-primitives.workspace = true
 spacetimedb-paths.workspace = true
 spacetimedb-sats = { workspace = true, features = ["serde"] }
 spacetimedb-schema.workspace = true
 spacetimedb-table.workspace = true
-spacetimedb-snapshot = { path = "../snapshot", default-features = false }
+spacetimedb-snapshot.workspace = true
 spacetimedb-execution.workspace = true
 
 anyhow = { workspace = true, features = ["backtrace"] }
@@ -39,9 +39,7 @@ thin-vec.workspace = true
 [features]
 # Print a warning when doing an unindexed `iter_by_col_range` on a large table.
 unindexed_iter_by_col_range_warn = []
-default = ["unindexed_iter_by_col_range_warn", "tokio"]
-tokio = ["spacetimedb-durability/tokio", "spacetimedb-snapshot/tokio"]
-simulation = ["spacetimedb-durability/simulation", "spacetimedb-snapshot/simulation"]
+default = ["unindexed_iter_by_col_range_warn"]
 # Enable test helpers and utils
 test = ["spacetimedb-commitlog/test", "spacetimedb-schema/test"]
 

crates/datastore/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "spacetimedb-dst"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+anyhow.workspace = true
+clap.workspace = true
+spacetimedb-datastore.workspace = true
+spacetimedb-commitlog.workspace = true
+spacetimedb-durability.workspace = true
+spacetimedb-engine.workspace = true
+spacetimedb-lib.workspace = true
+spacetimedb-primitives.workspace = true
+spacetimedb-runtime = { workspace = true, features = ["simulation"] }
+spacetimedb-sats.workspace = true
+spacetimedb-schema.workspace = true
+spacetimedb-table.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+
+[lints]
+workspace = true

crates/dst/Cargo.toml

@@ -0,0 +1,20 @@
+# SpacetimeDB DST
+
+Deterministic Simulation Testing framework for SpacetimeDB.
+
+## Test
+
+```sh
+cargo test -p spacetimedb-dst
+```
+
+## Run
+
+```sh
+cargo run -p spacetimedb-dst -- run --seed 42 --max-interactions 1000
+```
+
+Options:
+
+- `--seed <u64>` — RNG seed (defaults to wall-clock nanos)
+- `--max-interactions <usize>` — interaction budget