[stable-2.13] ansible-test - Prefer unittest.mock for core.

(cherry picked from commit 81351022d8)

Co-authored-by: Matt Clay <matt@mystile.com>

changelogs/fragments/ansible-test-ansible-core-mock.yml

@@ -0,0 +1,3 @@
+minor_changes:
+  - ansible-test - Avoid using the ``mock_use_standalone_module`` setting for ``pytest`` when running ansible-core unit tests.
+                   This has no effect on unit tests for collections.

test/lib/ansible_test/_data/pytest/config/ansible-core.ini

@@ -0,0 +1,4 @@
+[pytest]
+xfail_strict = true
+# avoid using 'mock_use_standalone_module = true' so package maintainers can avoid packaging 'mock'
+junit_family = xunit1

test/lib/ansible_test/_internal/commands/units/__init__.py

@@ -234,6 +234,11 @@ def command_units(args):  # type: (UnitsConfig) -> None
     if args.requirements_mode == 'only':
         sys.exit()
 
+    if data_context().content.is_ansible:
+        config_name = 'ansible-core.ini'
+    else:
+        config_name = 'default.ini'
+
     for test_context, python, paths, env in test_sets:
         cmd = [
             'pytest',
@@ -243,7 +248,7 @@ def command_units(args):  # type: (UnitsConfig) -> None
             '--color',
             'yes' if args.color else 'no',
             '-p', 'no:cacheprovider',
-            '-c', os.path.join(ANSIBLE_TEST_DATA_ROOT, 'pytest.ini'),
+            '-c', os.path.join(ANSIBLE_TEST_DATA_ROOT, 'pytest', 'config', config_name),
             '--junit-xml', os.path.join(ResultType.JUNIT.path, 'python%s-%s-units.xml' % (python.version, test_context)),
             '--strict-markers',  # added in pytest 4.5.0
             '--rootdir', data_context().content.root,