monkeypatch for sys.path; comments and param ids

Author: rcomer

docs/gallery_tests/conftest.py

@@ -6,35 +6,12 @@
 
 """Pytest fixtures for the gallery tests."""
 
-import pathlib
-import sys
 
 import matplotlib.pyplot as plt
 import pytest
 
 import iris
 
-CURRENT_DIR = pathlib.Path(__file__).resolve()
-GALLERY_DIR = CURRENT_DIR.parents[1] / "gallery_code"
-GALLERY_DIRECTORIES = [
-    str(path) for path in GALLERY_DIR.iterdir() if path.is_dir()
-]
-
-
-@pytest.fixture
-def add_gallery_to_path():
-    """
-    Creates a fixture which can be used to add the iris gallery to the
-    PYTHONPATH. The gallery entries are only importable throughout the lifetime
-    of the test.
-
-    """
-    orig_sys_path = sys.path
-    sys.path = sys.path[:]
-    sys.path += GALLERY_DIRECTORIES
-    yield
-    sys.path = orig_sys_path
-
 
 @pytest.fixture
 def image_setup_teardown():

docs/gallery_tests/test_gallery_examples.py

@@ -5,38 +5,53 @@
 # licensing details.
 
 import importlib
+import pathlib
 
 import matplotlib.pyplot as plt
 import pytest
 
 from iris.tests import check_graphic
 
-from .conftest import GALLERY_DIR
-
 
 def gallery_examples():
-    """Generator to yield all current gallery examples."""
-    for example_file in GALLERY_DIR.glob("*/plot*.py"):
-        yield example_file.stem
+    """
+    Generator to yield all current gallery examples and their containing
+    directories.
+
+    """
+    current_dir = pathlib.Path(__file__).resolve()
+    gallery_dir = current_dir.parents[1] / "gallery_code"
+    for example_file in gallery_dir.glob("*/plot*.py"):
+        yield example_file.parent, example_file.stem
 
 
 @pytest.mark.filterwarnings("error::iris.IrisDeprecation")
-@pytest.mark.parametrize("example_code", gallery_examples())
+@pytest.mark.parametrize("example", gallery_examples(), ids=lambda arg: arg[1])
 def test_plot_example(
-    example_code,
-    add_gallery_to_path,
+    example,
     image_setup_teardown,
     iris_future_defaults,
     monkeypatch,
 ):
+    """Test that all figures from example code match KGO."""
+
+    example_dir, example_code = example
+
+    # Replace pyplot.show with a function that does nothing, so all figures from the
+    # example are still open after it runs.
     def no_show():
         pass
 
     monkeypatch.setattr(plt, "show", no_show)
 
+    # Add example code to sys.path and import it.
+    monkeypatch.syspath_prepend(example_dir)
     module = importlib.import_module(example_code)
 
+    # Run example.
     module.main()
+    # Loop through open figures and set each to be the current figure so check_graphic
+    # will find it.
     for fig_num in plt.get_fignums():
         plt.figure(fig_num)
         image_id = f"gallery_tests.test_{example_code}.{fig_num - 1}"