Multi-process the tests. (#70)

.github/workflows/ci.yml

@@ -78,7 +78,7 @@ jobs:
         uses: quantco/pytest-action@v2
         with:
           report-title: Unit Tests - ${{ matrix.os == 'ubuntu-latest' && 'Linux' || 'Windows' }} - Python ${{ matrix.python-version }}
-          custom-arguments: --cov=metalearners --cov-report=xml --cov-report term-missing --color=yes
+          custom-arguments: -n auto --cov=metalearners --cov-report=xml --cov-report term-missing --color=yes
       - name: Upload coverage reports to Codecov
         uses: codecov/[email protected]
         with:

environment.yml

@@ -23,6 +23,7 @@ dependencies:
   # Testing
   - pytest >=6 # Adds --import-mode option
   - pytest-cov
+  - pytest-xdist
   ##  Numerical
   # First version to add the return_indices parameter to cross_validate.
   - scikit-learn>=1.3