1 files changed, 23 insertions, 0 deletions
diff --git a/smart_home/thermometers.py b/smart_home/thermometers.py
index 73117bc..4531c61 100644
--- a/smart_home/thermometers.py
+++ b/smart_home/thermometers.py
@@ -28,6 +28,22 @@ class ThermometerRegistry(object):
         }
 
     def read_temperature(self, location: str, *, convert_to_fahrenheit=False) -> Optional[float]:
+        """Read the current value of a thermometer (in celsius unless
+        convert_to_fahrenheit is True) and return it.  Return None on
+        error.
+
+        >>> registry = ThermometerRegistry()
+        >>> registry.read_temperature('unknown') is None
+        True
+
+        >>> temp = registry.read_temperature('house_computer_closet')
+        >>> temp is None
+        False
+        >>> temp > 0.0
+        True
+
+        """
+
         record = self.thermometers.get(location, None)
         if record is None:
             logger.error(
@@ -36,6 +52,7 @@ class ThermometerRegistry(object):
                 self.thermometers.keys(),
             )
             return None
+
         url = f'http://{record[0]}/~pi/{record[1]}'
         logger.debug('Constructed URL: %s', url)
         try:
@@ -54,3 +71,9 @@ class ThermometerRegistry(object):
             if www is not None:
                 www.close()
         return temp
+
+
+if __name__ == '__main__':
+    import doctest
+
+    doctest.testmod()