Add ut for envs.py (#2131)

What this PR does / why we need it?
test vllm_ascend/envs.py contains environment variables defination

Does this PR introduce any user-facing change?
N/A

How was this patch tested?
CI passed with new added test.

vLLM version: v0.10.0
vLLM main:
9532a6d563

- vLLM version: v0.10.0
- vLLM main:
b4e081cb15

---------

Signed-off-by: chengyuan <chengyuan27@huawei.com>
Co-authored-by: chengyuan <chengyuan27@huawei.com>

tests/ut/test_envs.py

@@ -0,0 +1,61 @@
+#
+# 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.
+# This file is a part of the vllm-ascend project.
+
+import inspect
+import os
+
+from tests.ut.base import TestBase
+from vllm_ascend import envs
+
+
+class TestEnvVariables(TestBase):
+
+    def setUp(self):
+        self.env_vars = list(envs.env_variables.keys())
+
+    def test_env_vars_behavior(self):
+        for var_name in self.env_vars:
+            with self.subTest(var=var_name):
+                original_val = os.environ.get(var_name)
+                var_handler = envs.env_variables[var_name]
+
+                try:
+                    if var_name in os.environ:
+                        del os.environ[var_name]
+                    self.assertEqual(getattr(envs, var_name), var_handler())
+
+                    handler_source = inspect.getsource(var_handler)
+                    if 'int(' in handler_source:
+                        test_vals = ["123", "456"]
+                    elif 'bool(int(' in handler_source:
+                        test_vals = ["0", "1"]
+                    else:
+                        test_vals = [f"test_{var_name}", f"custom_{var_name}"]
+
+                    for test_val in test_vals:
+                        os.environ[var_name] = test_val
+                        self.assertEqual(getattr(envs, var_name),
+                                         var_handler())
+
+                finally:
+                    if original_val is None:
+                        os.environ.pop(var_name, None)
+                    else:
+                        os.environ[var_name] = original_val
+
+    def test_dir_and_getattr(self):
+        self.assertEqual(sorted(envs.__dir__()), sorted(self.env_vars))
+        for var_name in self.env_vars:
+            with self.subTest(var=var_name):
+                getattr(envs, var_name)