[Android] Fix environment variable handling in devil_env.

build/android/devil/devil_env_test.py

+#!/usr/bin/env python
+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# pylint: disable=protected-access
+
+import logging
+import sys
+import unittest
+
+from devil import devil_env
+
+_sys_path_before = list(sys.path)
+with devil_env.SysPath(devil_env.config.LocalPath('pymock')):
+  _sys_path_with_pymock = list(sys.path)
+  import mock # pylint: disable=import-error
+_sys_path_after = list(sys.path)
+
+class DevilEnvTest(unittest.TestCase):
+
+  def testSysPath(self):
+    self.assertEquals(_sys_path_before, _sys_path_after)
+    self.assertEquals(
+        _sys_path_before + [devil_env.config.LocalPath('pymock')],
+        _sys_path_with_pymock)
+
+  def testGetEnvironmentVariableConfig_configType(self):
+    with mock.patch('os.environ.get',
+                    mock.Mock(side_effect=lambda _env_var: None)):
+      env_config = devil_env._GetEnvironmentVariableConfig()
+    self.assertEquals('BaseConfig', env_config.get('config_type'))
+
+  def testGetEnvironmentVariableConfig_noEnv(self):
+    with mock.patch('os.environ.get',
+                    mock.Mock(side_effect=lambda _env_var: None)):
+      env_config = devil_env._GetEnvironmentVariableConfig()
+    self.assertEquals({}, env_config.get('dependencies'))
+
+  def testGetEnvironmentVariableConfig_adbPath(self):
+    def mock_environment(env_var):
+      return '/my/fake/adb/path' if env_var == 'ADB_PATH' else None
+
+    with mock.patch('os.environ.get',
+                    mock.Mock(side_effect=mock_environment)):
+      env_config = devil_env._GetEnvironmentVariableConfig()
+    self.assertEquals(
+        {
+          'adb': {
+            'file_info': {
+              'android_linux2': {
+                'local_paths': ['/my/fake/adb/path'],
+              },
+            },
+          },
+        },
+        env_config.get('dependencies'))
+
+
+if __name__ == '__main__':
+  logging.getLogger().setLevel(logging.DEBUG)
+  unittest.main(verbosity=2)