From 84865d16dc99a8a491e3973edb4eccc8d6df5018 Mon Sep 17 00:00:00 2001
From: Russell Martin <rmartin16@gmail.com>
Date: Sat, 29 Apr 2023 01:57:28 -0400
Subject: [PATCH] Run `tox` tests in parallel

---
 changes/1247.misc.rst | 1 +
 pyproject.toml        | 2 ++
 setup.cfg             | 2 ++
 tests/conftest.py     | 2 +-
 tox.ini               | 7 +++++--
 5 files changed, 11 insertions(+), 3 deletions(-)
 create mode 100644 changes/1247.misc.rst

diff --git a/changes/1247.misc.rst b/changes/1247.misc.rst
new file mode 100644
index 000000000..b6ef90572
--- /dev/null
+++ b/changes/1247.misc.rst
@@ -0,0 +1 @@
+Python tests are now run in parallel via ``tox``.
diff --git a/pyproject.toml b/pyproject.toml
index 9c1d2e449..6b24450c0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,7 +3,9 @@ requires = ["setuptools>=60", "setuptools_scm[toml]>=7.0"]
 build-backend = "setuptools.build_meta"
 
 [tool.coverage.run]
+concurrency = ["multiprocessing", "thread"]
 parallel = true
+sigterm = true
 branch = true
 relative_files = true
 source_pkgs = ["briefcase"]
diff --git a/setup.cfg b/setup.cfg
index 62ccd3023..448c866a4 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -91,8 +91,10 @@ install_requires =
 # ensure environment consistency.
 dev =
     coverage[toml] == 7.2.3
+    coverage-enable-subprocess == 1.0
     pre-commit == 3.2.2
     pytest == 7.3.1
+    pytest-xdist == 3.2.1
     setuptools_scm[toml] == 7.1.0
     tox == 4.4.12
 docs =
diff --git a/tests/conftest.py b/tests/conftest.py
index 7bacd6765..b7ef8d62f 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -55,7 +55,7 @@ def no_print(monkeypatch):
 
 @pytest.fixture
 def sleep_zero(monkeypatch):
-    """Replace all calls to ``time.sleep(x)`` with ``time.sleep(0)."""
+    """Replace all calls to ``time.sleep(x)`` with ``time.sleep(0)``."""
     monkeypatch.setattr(time, "sleep", lambda x: _sleep(0))
 
 
diff --git a/tox.ini b/tox.ini
index 4c0099bba..3bd4585e5 100644
--- a/tox.ini
+++ b/tox.ini
@@ -7,8 +7,11 @@ download = True
 # The leading comma generates the "py" environment.
 [testenv:py{,38,39,310,311,312}{,-coverage}]
 passenv =
-    # LOCALAPPDATA is needed to test data directory creation on Windows.
+    # Needed on Windows to test data directory creation
     LOCALAPPDATA
+setenv =
+    # Start Python such that coverage is possible in subprocesses
+    COVERAGE_PROCESS_START = {toxinidir}/pyproject.toml
 extras =
     dev
 # 2023-04-22 The virtualenv used by Tox has pip 23.1 pinned into it
@@ -16,7 +19,7 @@ extras =
 # need to force pip to be updated.
 download = True
 commands =
-    python -m coverage run -m pytest -vv {posargs}
+    python -m coverage run -m pytest {posargs:-n auto -vv}
     coverage : python -m coverage combine
     coverage : python -m coverage report