Add unit test for shell formatter

This is in prepration for changing the behavior to escape double quotes.

Change-Id: Ib82511d066d70a1603b80ba8680b005e00113483
Related-Bug: #1269908

cliff/tests/test_formatters_shell.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python
+from six import StringIO
+
+from cliff.formatters import shell
+
+import mock
+
+
+def test_shell_formatter():
+    sf = shell.ShellFormatter()
+    c = ('a', 'b', 'c')
+    d = ('A', 'B', 'C')
+    expected = 'a="A"\nb="B"\n'
+    output = StringIO()
+    args = mock.Mock()
+    args.variables = ['a', 'b']
+    args.prefix = ''
+    sf.emit_one(c, d, output, args)
+    actual = output.getvalue()
+    assert expected == actual