Cosmetic clean-up of the pytest fixtures in tests/unit/conftest.py

tests/unit/conftest.py

@@ -1,4 +1,15 @@
-"""tests/unit/conftest.py: pytest fixtures for unit-testing functions in the xen-bugtool script"""
+"""tests/unit/conftest.py: pytest fixtures for unit-testing xen-bugtool
+
+Introduction to fixtures:
+https://docs.pytest.org/en/8.0.x/fixture.html
+
+How to use fixtures:
+https://docs.pytest.org/en/8.0.x/how-to/fixtures.html
+
+The full documentation on fixtures:
+https://docs.pytest.org/en/8.0.x/reference/fixtures.html
+"""
+
 from __future__ import print_function
 
 import os
@@ -10,61 +21,58 @@
 
 @pytest.fixture(scope="function")
 def builtins():
-    """
-    Pytest fixture to return the name of the built-in module.
-    The built-in module provides the built-in functions, exceptions, etc.
-    It is needed to replace built-in functions like open() with a new mock.
-
-    :returns (str): The name of the built-in module.
-    """
-    if sys.version_info < (3,):
-        return "__builtin__"  # pragma: no cover
-    return "builtins"
+    """Provide the builtins module name for Python 2.x and Python 3.x"""
+    return "__builtin__" if sys.version_info < (3,) else "builtins"
 
 
 @pytest.fixture(scope="session")
 def testdir():
-    """Test fixture to get the directory of the unit test for finding other files relative to it"""
+    """Test fixture to provide the directory of the dom0 template directory"""
     return os.path.dirname(__file__)
 
 
 @pytest.fixture(scope="session")
 def dom0_template(testdir):
-    """Test fixture to get the directory of the dom0 template and adding it's /usr/sbin to the PATH"""
-    dom0_root_dir = testdir + "/../integration/dom0-template"
-    return dom0_root_dir
+    """Test fixture to get the directory of the dom0 template"""
+    return testdir + "/../integration/dom0-template"
 
 
 @pytest.fixture(scope="session")
 def imported_bugtool(testdir, dom0_template):
-    """Test fixture to import the xen-bugtool script as a module for executing unit tests on functions"""
+    """Fixture to provide the xen-bugtool script as a module for unit tests"""
 
-    # This uses the deprecated imp module because it needs also to run with Python2.7 for now:
     def import_from_file(module_name, file_path):
         if sys.version_info.major == 2:  # pragma: no cover
-            import imp  # pylint: disable=deprecated-module  # pyright: ignore[reportMissingImports]
+            # Python 2.7, use the deprecated imp module (no alternative)
+            # pylint: disable-next=deprecated-module
+            import imp  # pyright: ignore[reportMissingImports]
 
-            return imp.load_source(module_name, file_path)
+            module = imp.load_source(module_name, file_path)
+
+            # Prevent other code from importing the same module again:
+            sys.modules[module_name] = module
+            return module
         else:
-            # Py3.11+: Importing Python source code from a script without the .py extension:
-            # https://gist.github.com/bernhardkaindl/1aaa04ea925fdc36c40d031491957fd3:
             from importlib import machinery, util
 
             loader = machinery.SourceFileLoader(module_name, file_path)
             spec = util.spec_from_loader(module_name, loader)
             assert spec
             assert spec.loader
             module = util.module_from_spec(spec)
-            # Probably a good idea to add manually imported module stored in sys.modules
+
+            # Prevent other code from importing the same module again:
             sys.modules[module_name] = module
             spec.loader.exec_module(module)
             return module
 
     bugtool = import_from_file("xen-bugtool", testdir + "/../../xen-bugtool")
     bugtool.ProcOutput.debug = True
+
     # Prepend tests/mocks to force the use of our mock xen.lowlevel.xc module:
     sys.path.insert(0, testdir + "/../mocks")
     os.environ["PATH"] = dom0_template + "/usr/sbin"  # for modinfo, mdadm, etc
+
     return bugtool
 
 
@@ -74,7 +82,12 @@ def bugtool(imported_bugtool):
     # Init import_bugtool.data, so each unit test function gets it pristine:
     imported_bugtool.data = {}
     sys.argv = ["xen-bugtool", "--unlimited"]
-    return imported_bugtool
+
+    yield imported_bugtool  # provide the bugtool to the test function
+
+    # Cleanup the bugtool data dict after each test as tests may modify it:
+    imported_bugtool.data = {}
+    sys.argv = ["xen-bugtool", "--unlimited"]
 
 
 @pytest.fixture(scope="function")