Configure pytest to use importlib import mode

By default, running `pytest` prepends the source directory to the Python
path, since that's where the `tests` package is.  That causes Python to
import `openslide` from the source directory instead of using the
installed copy, and this fails because the source directory doesn't have
the compiled extension module.  Configure pytest not to change the Python
path, as recommended by pytest docs:

https://docs.pytest.org/en/7.1.x/explanation/goodpractices.html#choosing-an-import-mode

Then, manually set the Python path to allow tests to load common code.

Signed-off-by: Benjamin Gilbert <bgilbert@cs.cmu.edu>

Author: bgilbert

.github/workflows/python.yml

@@ -53,7 +53,7 @@ jobs:
           ;;
         esac
     - name: Install
-      run: pip install -e .
+      run: pip install .
     - name: Run tests
       run: pytest -v
     - name: Tile slide

MANIFEST.in

@@ -1,4 +1,4 @@
-include *.md
+include *.md pytest.ini
 recursive-include doc *.py *.rst
 recursive-include examples *.html *.js *.png *.py
 recursive-include tests *.png *.py *.svs *.tiff

pytest.ini

@@ -0,0 +1,7 @@
+[pytest]
+minversion = 6.0
+# don't try to import openslide from the source directory, since it doesn't
+# have the compiled extension module
+addopts = --import-mode importlib
+# allow tests to import common module
+pythonpath = tests