feat: add simulation clocks and VM transitions

tests/unit/test_clock.py

@@ -0,0 +1,28 @@
+"""Simulation clock behavior."""
+
+import asyncio
+from datetime import UTC, datetime
+
+import pytest
+
+from app.simulation.clock import AcceleratedClock, ManualClock
+
+
+async def test_manual_clock_releases_sleep_only_after_advance() -> None:
+    clock = ManualClock(datetime(2026, 1, 1, tzinfo=UTC))
+    sleeper = asyncio.create_task(clock.sleep(10))
+    await asyncio.sleep(0)
+    assert not sleeper.done()
+
+    await clock.advance(9)
+    assert not sleeper.done()
+    await clock.advance(1)
+    await sleeper
+    assert await clock.now() == datetime(2026, 1, 1, 0, 0, 10, tzinfo=UTC)
+
+
+def test_clocks_reject_invalid_configuration() -> None:
+    with pytest.raises(ValueError):
+        AcceleratedClock(0)
+    with pytest.raises(ValueError):
+        ManualClock(datetime(2026, 1, 1))

tests/unit/test_transitions.py

@@ -0,0 +1,46 @@
+"""VM state-machine and deterministic fault properties."""
+
+import pytest
+from hypothesis import given
+from hypothesis import strategies as st
+
+from app.simulation.scenarios import FaultContext, FaultRule, matches
+from app.simulation.transitions import InvalidTransitionError, VmState, plan_transition
+
+
+@pytest.mark.parametrize(
+    ("state", "operation", "final"),
+    [
+        (VmState.STOPPED, "start", VmState.RUNNING),
+        (VmState.RUNNING, "stop", VmState.STOPPED),
+        (VmState.RUNNING, "pause", VmState.PAUSED),
+        (VmState.PAUSED, "resume", VmState.RUNNING),
+        (VmState.RUNNING, "snapshot", VmState.RUNNING),
+        (VmState.STOPPED, "migrate", VmState.STOPPED),
+    ],
+)
+def test_valid_transitions(state: VmState, operation: str, final: VmState) -> None:
+    transition = plan_transition(state, operation)
+    assert transition.before is state
+    assert transition.after is final
+    assert transition.intermediate is not state
+
+
+@given(st.sampled_from(tuple(VmState)), st.text(min_size=1, max_size=12))
+def test_transition_result_is_declared_or_rejected(state: VmState, operation: str) -> None:
+    try:
+        transition = plan_transition(state, operation)
+    except InvalidTransitionError:
+        return
+    assert transition.before is state
+
+
+def test_fault_evaluation_is_seeded_and_filtered() -> None:
+    context = FaultContext("POST", "/nodes/pve1/qemu/100/status/start", node="pve1")
+    certain = FaultRule("task-failure", method="POST", node="pve1")
+    impossible = FaultRule("task-failure", probability=0)
+
+    assert matches(certain, context, seed=42)
+    assert not matches(impossible, context, seed=42)
+    probabilistic = FaultRule("task-failure", probability=0.5)
+    assert matches(probabilistic, context, 42) == matches(probabilistic, context, 42)