Add a very simple testcase

tools/rosbag/CMakeLists.txt

@@ -58,3 +58,7 @@ catkin_install_python(PROGRAMS
   scripts/savemsg.py
   scripts/topic_renamer.py
   DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION})
+
+if(CATKIN_ENABLE_TESTING)
+  catkin_add_nosetests(test)
+endif()

tools/rosbag/test/test_roundtrip.py

@@ -0,0 +1,75 @@
+import unittest
+import tempfile
+import os
+
+import rosbag
+import rospy
+
+BAG_DIR = tempfile.mkdtemp(prefix='rosbag_tests')
+
+class TestRoundTrip(unittest.TestCase):
+    def _write_simple_bag(self, name):
+        from std_msgs.msg import Int32, String
+
+        with rosbag.Bag(name, 'w') as bag:
+            s = String(data='foo')
+            i = Int32(data=42)
+
+            bag.write('chatter', s)
+            bag.write('numbers', i)
+
+    def _fname(self, name):
+        return os.path.join(BAG_DIR, name)
+
+    def test_value_equality(self):
+        fname = self._fname('test_value_equality.bag')
+
+        self._write_simple_bag(fname)
+
+        with rosbag.Bag(fname) as bag:
+            numbers = list(bag.read_messages('numbers'))
+            chatter = list(bag.read_messages('chatter'))
+
+        self.assertEqual(len(numbers), 1)
+        self.assertEqual(len(chatter), 1)
+
+        numbers = numbers[0]
+        chatter = chatter[0]
+
+        # channel names
+        self.assertEqual(numbers[0], 'numbers')
+        self.assertEqual(chatter[0], 'chatter')
+
+        # values
+        self.assertEqual(numbers[1].data, 42)
+        self.assertEqual(chatter[1].data, 'foo')
+
+    @unittest.expectedFailure
+    def test_type_equality(self):
+        fname = self._fname('test_type_equality.bag')
+
+        from std_msgs.msg import Int32, String
+
+        self._write_simple_bag(fname)
+
+        with rosbag.Bag(fname) as bag:
+            numbers = next(bag.read_messages('numbers'))
+            chatter = next(bag.read_messages('chatter'))
+
+        self.assertEqual(numbers[1].__class__, Int32)
+        self.assertEqual(chatter[1].__class__, String)
+
+    @unittest.expectedFailure
+    def test_type_isinstance(self):
+        fname = self._fname('test_type_isinstance.bag')
+
+        from std_msgs.msg import Int32, String
+
+        self._write_simple_bag(fname)
+
+        with rosbag.Bag(fname) as bag:
+            numbers = next(bag.read_messages('numbers'))
+            chatter = next(bag.read_messages('chatter'))
+
+        self.assertIsInstance(numbers[1], Int32)
+        self.assertIsInstance(chatter[1], String)