new file mode 100644
--- /dev/null
+++ b/tests/test_diff.py
@@ -0,0 +1,34 @@
+from mercurial import ui
+
+import diff_cmd
+
+import test_util
+
+expected_diff_output = '''Index: alpha
+===================================================================
+--- alpha\t(revision 3)
++++ alpha\t(working copy)
+@@ -1,1 +1,3 @@
+-file: alpha
++alpha
++
++added line
+Index: foo
+===================================================================
+new file mode 100644
+--- foo\t(revision 0)
++++ foo\t(working copy)
+@@ -0,0 +1,1 @@
++This is missing a newline.
+\ No newline at end of file
+'''
+
+class DiffTests(test_util.TestBase):
+    def test_diff_output(self):
+        self._load_fixture_and_fetch('two_revs.svndump')
+        self.commitchanges([('foo', 'foo', 'This is missing a newline.'),
+                            ('alpha', 'alpha', 'alpha\n\nadded line\n'),
+                            ])
+        u = ui.ui()
+        diff_cmd.diff_command(u, self.repo, self.wc_path)
+        self.assertEqual(u.stream.getvalue(), expected_diff_output)