Run tests in parallel when possible

Author: ragibson

.github/workflows/python-package.yml

@@ -31,7 +31,7 @@ jobs:
 
           pip install .
 
-          pip install cython flake8 pytest
+          pip install cython flake8 pytest pytest-xdist
       - name: Lint with flake8
         run: |
           source env/bin/activate
@@ -42,4 +42,4 @@ jobs:
       - name: Test with pytest
         run: |
           source env/bin/activate
-          pytest tests/
+          pytest -n auto -m "not serial" tests/ && pytest -m "serial" tests/

tests/pytest.ini

@@ -0,0 +1,3 @@
+[pytest]
+markers =
+    serial: mark test that should be run serially

tests/test_parallel_leiden_performance.py

@@ -9,6 +9,7 @@
 import igraph as ig
 import numpy as np
 import psutil
+import pytest
 import unittest
 import warnings
 
@@ -59,6 +60,7 @@ def determine_target_parallelization_speedup(num_calculations=32):
     return num_pool_calculations / num_calculations * base_duration / pool_duration
 
 
+@pytest.mark.serial  # these tests have to run serially for the parallel performance comparisons to make sense
 class TestParallelLeidenPerformance(unittest.TestCase):
     @staticmethod
     def run_singlelayer_graph_parallelization(G, gammas):