add test for uses_services get_platform rule

Author: cognifloyd

pants-plugins/uses_services/BUILD

@@ -1 +1,5 @@
 python_sources()
+
+python_tests(
+    name="tests",
+)

pants-plugins/uses_services/platform_rules_test.py

@@ -0,0 +1,49 @@
+# Copyright 2023 The StackStorm Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from __future__ import annotations
+
+import dataclasses
+
+import pytest
+
+from pants.testutil.rule_runner import QueryRule, RuleRunner
+
+from .platform_rules import Platform, rules as platform_rules
+
+
+@pytest.fixture
+def rule_runner() -> RuleRunner:
+    return RuleRunner(
+        rules=[
+            *platform_rules(),
+            QueryRule(Platform, ()),
+        ],
+        target_types=[],
+    )
+
+
+def test_get_platform(rule_runner: RuleRunner) -> None:
+    rule_runner.set_options(
+        ["--backend-packages=uses_services"],
+        env_inherit={"PATH", "PYENV_ROOT", "HOME"},
+    )
+
+    platform = rule_runner.request(Platform, ())
+
+    assert isinstance(platform, Platform)
+    assert dataclasses.is_dataclass(platform)
+    # there isn't a good way to inject mocks into the script that
+    # the rule_runner runs in a venv. So, there isn't a nice way
+    # to test the values of the Platform fields as people could
+    # run tests on any platform.