Adds create_reader/create_writer tests.

tests/test_registry.py

@@ -0,0 +1,18 @@
+from bonobo.nodes import CsvReader, JsonReader, CsvWriter, JsonWriter
+from bonobo import create_reader, create_writer
+
+
+def test_create_reader():
+    t = create_reader('foo.csv')
+    assert isinstance(t, CsvReader)
+
+    t = create_reader('foo.txt', format='json')
+    assert isinstance(t, JsonReader)
+
+
+def test_create_writer():
+    t = create_writer('foo.csv')
+    assert isinstance(t, CsvWriter)
+
+    t = create_writer('foo.txt', format='json')
+    assert isinstance(t, JsonWriter)