Automatically run slow tests when main is involved. (#438)

In addition, this PR limits the slow test to Windows and Python 3.10.
The choices are somewhat arbitrary, my thought was to test the setup not
covered as much through use by the devs.

Author: vpratz

.github/workflows/tests.yaml

@@ -73,8 +73,11 @@ jobs:
           pytest -x -m "not slow"
 
       - name: Run Slow Tests
-        # run all slow tests only on manual trigger
-        if: github.event_name == 'workflow_dispatch'
+        # Run slow tests on manual trigger and pushes/PRs to main.
+        # Limit to one OS and Python version to save compute.
+        # Multiline if statements are weird, https://github.com/orgs/community/discussions/25641,
+        # but feel free to convert it.
+        if: ${{ ((github.event_name == 'workflow_dispatch') || (github.event_name == 'push' && github.ref_name == 'main') || (github.event_name == 'pull_request' && github.base_ref == 'main')) && ((matrix.os == 'windows-latest') && (matrix.python-version == '3.10')) }}
         run: |
           pytest -m "slow"