allocrunner: add test for missing alloc dir

Author: rodrigol-chan

client/allocrunner/alloc_runner_test.go

@@ -1422,6 +1422,33 @@ func TestAllocRunner_Restore_LifecycleHooks(t *testing.T) {
 	tasklifecycle.RequireTaskAllowed(t, ar2.taskCoordinator, ar2.tasks["poststart"].Task())
 }
 
+// TestAllocRunner_Restore_MissingAllocDir asserts that Restore() fails when the
+// allocation directory is missing, which can happen if allocation storage is
+// ephemeral (e.g., tmpfs or cloud local SSDs).
+func TestAllocRunner_Restore_MissingAllocDir(t *testing.T) {
+	ci.Parallel(t)
+
+	alloc := mock.Alloc()
+	conf, cleanup := testAllocRunnerConfig(t, alloc)
+	defer cleanup()
+
+	arIface, err := NewAllocRunner(conf)
+	must.NoError(t, err)
+	ar := arIface.(*allocRunner)
+
+	// Get the allocation directory path before deleting it
+	allocDirPath := ar.allocDir.AllocDirPath()
+
+	// Remove the allocation directory to simulate ephemeral storage being deleted
+	err = os.RemoveAll(allocDirPath)
+	must.NoError(t, err)
+
+	// Call Restore() and verify it fails with appropriate error
+	err = ar.Restore()
+	must.Error(t, err)
+	must.ErrorIs(t, err, os.ErrNotExist)
+}
+
 func TestAllocRunner_Update_Semantics(t *testing.T) {
 	ci.Parallel(t)
 	require := require.New(t)