feat: add basic QEMU and task vertical slice

tests/unit/test_qemu_task.py

@@ -0,0 +1,84 @@
+"""QEMU worker transition semantics."""
+
+import uuid
+from datetime import UTC, datetime
+from typing import cast
+
+from app.simulation.clock import Clock
+from app.tasks.qemu import qemu_handler
+from app.tasks.repository import Task, TaskRepository
+
+
+class ImmediateClock:
+    async def now(self) -> datetime:
+        return datetime(2026, 1, 1, tzinfo=UTC)
+
+    async def sleep(self, seconds: float) -> None:
+        assert seconds == 1.0
+
+
+class Connection:
+    def __init__(self) -> None:
+        self.states: list[str] = []
+
+    async def fetchrow(self, sql: str, resource_id: uuid.UUID) -> dict[str, object]:
+        del sql, resource_id
+        return {"state": '{"status":"stopped"}'}
+
+    async def execute(self, sql: str, resource_id: uuid.UUID, state: str) -> str:
+        del sql, resource_id
+        self.states.append(state)
+        return "UPDATE 1"
+
+
+class Acquire:
+    def __init__(self, connection: Connection) -> None:
+        self.connection = connection
+
+    async def __aenter__(self) -> Connection:
+        return self.connection
+
+    async def __aexit__(self, *args: object) -> None:
+        return None
+
+
+class Pool:
+    def __init__(self, connection: Connection) -> None:
+        self.connection = connection
+
+    def acquire(self) -> Acquire:
+        return Acquire(self.connection)
+
+
+class Repository:
+    def __init__(self) -> None:
+        self.connection = Connection()
+        self.pool = Pool(self.connection)
+        self.logs: list[str] = []
+
+    async def append_log(self, task_id: uuid.UUID, message: str) -> None:
+        del task_id
+        self.logs.append(message)
+
+
+async def test_qemu_worker_applies_intermediate_and_final_states() -> None:
+    repository = Repository()
+    task = Task(
+        uuid.uuid4(),
+        "UPID:test",
+        "qemu-start",
+        "running",
+        {"resource_id": str(uuid.uuid4())},
+        0,
+        False,
+        1,
+    )
+
+    result = await qemu_handler(cast(TaskRepository, repository), cast(Clock, ImmediateClock()))(
+        task
+    )
+
+    assert result == {"status": "running"}
+    assert '"starting"' in repository.connection.states[0]
+    assert '"running"' in repository.connection.states[1]
+    assert repository.logs == ["VM start started", "VM start completed"]