File sensor (#7569)

* Add File sensor

* Use None and return

* Remove I/O

* Use less memory

* No traceback if file is empty

tests/components/sensor/test_file.py

@@ -0,0 +1,91 @@
+"""The tests for local file sensor platform."""
+import unittest
+from unittest.mock import Mock, patch
+
+# Using third party package because of a bug reading binary data in Python 3.4
+# https://bugs.python.org/issue23004
+from mock_open import MockOpen
+
+from homeassistant.setup import setup_component
+from homeassistant.const import STATE_UNKNOWN
+
+from tests.common import get_test_home_assistant
+
+
+class TestFileSensor(unittest.TestCase):
+    """Test the File sensor."""
+
+    def setup_method(self, method):
+        """Set up things to be run when tests are started."""
+        self.hass = get_test_home_assistant()
+
+    def teardown_method(self, method):
+        """Stop everything that was started."""
+        self.hass.stop()
+
+    @patch('os.path.isfile', Mock(return_value=True))
+    @patch('os.access', Mock(return_value=True))
+    def test_file_value(self):
+        """Test the File sensor."""
+        config = {
+            'sensor': {
+                'platform': 'file',
+                'name': 'file1',
+                'file_path': 'mock.file1',
+            }
+        }
+
+        m_open = MockOpen(read_data='43\n45\n21')
+        with patch('homeassistant.components.sensor.file.open', m_open,
+                   create=True):
+            assert setup_component(self.hass, 'sensor', config)
+            self.hass.block_till_done()
+
+        state = self.hass.states.get('sensor.file1')
+        self.assertEqual(state.state, '21')
+
+    @patch('os.path.isfile', Mock(return_value=True))
+    @patch('os.access', Mock(return_value=True))
+    def test_file_value_template(self):
+        """Test the File sensor with JSON entries."""
+        config = {
+            'sensor': {
+                'platform': 'file',
+                'name': 'file2',
+                'file_path': 'mock.file2',
+                'value_template': '{{ value_json.temperature }}',
+            }
+        }
+
+        data = '{"temperature": 29, "humidity": 31}\n' \
+               '{"temperature": 26, "humidity": 36}'
+
+        m_open = MockOpen(read_data=data)
+        with patch('homeassistant.components.sensor.file.open', m_open,
+                   create=True):
+            assert setup_component(self.hass, 'sensor', config)
+            self.hass.block_till_done()
+
+        state = self.hass.states.get('sensor.file2')
+        self.assertEqual(state.state, '26')
+
+    @patch('os.path.isfile', Mock(return_value=True))
+    @patch('os.access', Mock(return_value=True))
+    def test_file_empty(self):
+        """Test the File sensor with an empty file."""
+        config = {
+            'sensor': {
+                'platform': 'file',
+                'name': 'file3',
+                'file_path': 'mock.file',
+            }
+        }
+
+        m_open = MockOpen(read_data='')
+        with patch('homeassistant.components.sensor.file.open', m_open,
+                   create=True):
+            assert setup_component(self.hass, 'sensor', config)
+            self.hass.block_till_done()
+
+        state = self.hass.states.get('sensor.file3')
+        self.assertEqual(state.state, STATE_UNKNOWN)