From 160798b8638d3ff54680f3fb763f01cc5e809eaf Mon Sep 17 00:00:00 2001
From: Max Rossmannek <oss@zurich.ibm.com>
Date: Tue, 10 Sep 2024 11:41:47 +0200
Subject: [PATCH] fix: compatibility with Windows

---
 qiskit_addon_obp/backpropagation.py |  7 ++++++
 test/test_backpropagation.py        | 38 +++++++++++++++++------------
 test/utils/test_metadata.py         |  3 ++-
 3 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/qiskit_addon_obp/backpropagation.py b/qiskit_addon_obp/backpropagation.py
index 5df49fe..bbf22ba 100644
--- a/qiskit_addon_obp/backpropagation.py
+++ b/qiskit_addon_obp/backpropagation.py
@@ -17,6 +17,7 @@
 import copy
 import logging
 import signal
+import sys
 from collections.abc import Sequence
 
 from qiskit import QuantumCircuit
@@ -68,6 +69,9 @@ def backpropagate(
     the ``truncation_error_budget`` argument. Refer to the
     :func:`~qiskit_addon_obp.utils.truncating.setup_budget` documentation for more details.
 
+    .. warning::
+       The ``max_seconds`` argument is not available on Windows!
+
     Args:
         observables: The observable(s) onto which the circuit is backpropagated.
         slices: A sequence of ``QuantumCircuit`` objects representing a single circuit which
@@ -92,6 +96,7 @@ def backpropagate(
         - A metadata container.
 
     Raises:
+        RuntimeError: If the ``max_seconds`` argument is attempted to be used on Windows.
         ValueError: All observables and slices must act on equivalent numbers of qubits.
         ValueError: An input observable is larger than the constraints specified by ``operator_budget``.
         ValueError: ``operator_budget.max_paulis`` or ``operator_budget.max_qwc_groups`` is less than 1.
@@ -122,6 +127,8 @@ def backpropagate(
     )
 
     if max_seconds is not None:
+        if sys.platform == "win32":
+            raise RuntimeError("The `max_seconds` argument is not available on Windows.")
 
         def handle_timeout(signum, frame):
             raise TimeoutException()
diff --git a/test/test_backpropagation.py b/test/test_backpropagation.py
index b0e89f5..8b60f5a 100644
--- a/test/test_backpropagation.py
+++ b/test/test_backpropagation.py
@@ -12,6 +12,7 @@
 
 """Tests for operator backpropagation utility functions."""
 
+import sys
 import time
 import unittest
 from math import e
@@ -875,17 +876,21 @@ def test_backpropagate_multi(self):
                 backpropagate(obs, slices, operator_budget=op_budget)
 
     def test_backpropagate_timeout(self):
+        qc = QuantumCircuit(2)
+        qc.rx(0.1, 0)
+        qc.ry(0.1, 0)
+        qc.rz(0.1, 0)
+        qc.cx(0, 1)
+        slices = slice_by_depth(qc, 1)
+        obs = SparsePauliOp("IX")
+
+        on_win = sys.platform == "win32"
         with self.subTest("Actual timeout"):
-            qc = QuantumCircuit(2)
-            qc.rx(0.1, 0)
-            qc.ry(0.1, 0)
-            qc.rz(0.1, 0)
-            qc.cx(0, 1)
-            slices = slice_by_depth(qc, 1)
-            slices = 100_000 * slices
-            obs = SparsePauliOp("IX")
+            if on_win:
+                pytest.skip("Does not run on Windows")
+            many_slices = 100_000 * slices
             t1 = time.time()
-            _, new_qc, _ = backpropagate(obs, slices, max_seconds=1)
+            _, new_qc, _ = backpropagate(obs, many_slices, max_seconds=1)
             t2 = time.time()
 
             with self.subTest("Time should be less than 2 seconds"):
@@ -895,13 +900,8 @@ def test_backpropagate_timeout(self):
                 assert len(new_qc) > 0
 
         with self.subTest("Reset timeout"):
-            qc = QuantumCircuit(2)
-            qc.rx(0.1, 0)
-            qc.ry(0.1, 0)
-            qc.rz(0.1, 0)
-            qc.cx(0, 1)
-            slices = slice_by_depth(qc, 1)
-            obs = SparsePauliOp("IX")
+            if on_win:
+                pytest.skip("Does not run on Windows")
             t1 = time.time()
             _, new_qc, _ = backpropagate(obs, slices, max_seconds=1)
             t2 = time.time()
@@ -910,3 +910,9 @@ def test_backpropagate_timeout(self):
                 assert len(new_qc) == 0
 
             sleep(1)
+
+        with self.subTest("Handle windows"):
+            if not on_win:
+                pytest.skip("Only on Windows")
+            with self.assertRaises(RuntimeError):
+                _, _, _ = backpropagate(obs, slices, max_seconds=1)
diff --git a/test/utils/test_metadata.py b/test/utils/test_metadata.py
index 6ff0d09..52b0c6f 100644
--- a/test/utils/test_metadata.py
+++ b/test/utils/test_metadata.py
@@ -14,6 +14,7 @@
 
 from __future__ import annotations
 
+import sys
 import tempfile
 import unittest
 
@@ -170,7 +171,7 @@ def test_from_json(self):
         self.assertEqual(metadata, self.expected)
 
     def test_to_json(self):
-        with tempfile.NamedTemporaryFile() as file:
+        with tempfile.NamedTemporaryFile(delete=sys.platform != "win32") as file:
             self.expected.to_json(file.name, indent=2)
 
             with (