Better docstring, and a more distinctive example

ddt.py

@@ -30,9 +30,18 @@ def file_data(value):
 
     Should be added to methods of instances of ``unittest.TestCase``.
 
-    ``value`` should be a path relative to the directory that the file
+    ``value`` should be a path relative to the directory of the file
     containing the decorated ``unittest.TestCase``. The file
-    should contain a JSON encoded list of dicts with each dict containing a
+    should contain JSON encoded data, that can either be a list or a
+    dict.
+
+    In case of a list, each value in the list will correspond to one
+    test case, and the value will be concatenated to the test method
+    name.
+
+    In case of a dict, keys will be used as suffixes to the name of the
+    test case, and values will be fed as test data.
+
     ``test_name`` and a ``data`` key. The ``test_name`` value should
     be the name of the test and the value for the ``data`` key should
     be a list of data values.

test/mycode.py

@@ -9,3 +9,7 @@ def larger_than_two(value):
 
 def has_three_elements(value):
     return len(value) == 3
+
+
+def is_a_greeting(value):
+    return value in ['Hello', 'Goodbye']

test/test_example.py

@@ -1,6 +1,6 @@
 import unittest
 from ddt import ddt, data, file_data
-from .mycode import larger_than_two, has_three_elements
+from .mycode import larger_than_two, has_three_elements, is_a_greeting
 
 
 class mylist(list):
@@ -38,4 +38,4 @@ class FooTestCase(unittest.TestCase):
 
     @file_data('test_data_list.json')
     def test_file_data_list(self, value):
-        self.assertTrue(has_three_elements(value))
+        self.assertTrue(is_a_greeting(value))